Monarch Watch and the 2015 White House Easter Egg Roll

MEDIA CONTACT: Alanna Sobel
202-796-2538
asobel@nationalparks.org

FOR IMMEDIATE RELEASE

WASHINGTON (April 3, 2015) Monarch Watch announced today that it will contribute to the National Park Foundation, the official charity of America’s national parks, to support the 2015 White House Easter Egg Roll.

The White House Easter Egg Roll takes place in President’s Park on the South Lawn of the White House. This year’s theme, “#GimmeFive,” encourages Americans across the country to share five things they are doing to eat better, be more active, and lead a healthier life, and supports the First Lady’s Let’s Move! initiative to help kids grow up healthy and have the opportunity to reach their full potential.

Monarch Watch is meeting the #GimmeFive challenge by: 1) inspiring kids to get outside and garden for monarchs and other pollinators, 2) encouraging people to plant milkweeds to increase the monarch population, 3) helping people draw connections between pollinators and our food system, 4) teaching kids about the importance of native habitats and 5) spreading the love for butterflies.

In addition, the official White House Easter Eggs, sold by the National Park Foundation and benefiting America’s national parks, are available at easter.nationalparks.org.

Find more information about the National Park Foundation at www.nationalparks.org. Join the national park community by visiting www.facebook.com/nationalpark and www.twitter.com/goparks.

ABOUT MONARCH WATCH
Monarch Watch strives to provide the public with information about the biology of monarch butterflies and their spectacular migration, education about the need to create habitats for monarchs, and ways to use monarchs to further science education in schools. Monarch Watch leads the nationally recognized Monarch Waystation certification program and the Bring Back the Monarchs program, designed to address issue of restoring milkweeds to our landscape. Help Bring Back the Monarchs! Plant milkweed and nectar plants! Visit our website for more information: http://www.monarchwatch.org/

ABOUT THE NATIONAL PARK FOUNDATION
The National Park Foundation is the official charity of America’s national parks and nonprofit partner to the National Park Service. Chartered by Congress in 1967, the National Park Foundation raises private funds to help PROTECT more than 84 million acres of national parks through critical conservation and preservation efforts, CONNECT all Americans with their incomparable natural landscapes, vibrant culture and rich history, and INSPIRE the next generation of park stewards. Find out more and become a part of the national park community at www.nationalparks.org

Free Lecture: Bringing Nature Home

Douglas Tallamy, author of “Bringing Nature Home: How you can sustain wildlife with native plants” is coming to Lawrence, KS on March 21st. It promises to be an inspiring evening. Monarch Watch has taken the lead to bring Douglas to the University of Kansas and coordinate the event, with the sponsorship of several other amazing organizations. The flyer below is also available in PDF format – please feel free to print and distribute it. We’ve also created a Facebook event so please feel free to share that as well.

Filed under Events | Comments Off on Free Lecture: Bringing Nature Home

Monarch Conservation: Our Choices

In an earlier posting to this blog I commented on the “Petition to protect the monarch butterfly (Danaus plexippus plexippus) under the Endangered Species Act” (see Commentary: Recent Petition to Protect the Monarch Butterfly). The commentary included notes about the petition, the distinction between endangered and threatened (a distinction frequently ignored by the press), and the process a petition goes through from the time of submission to acceptance or rejection. I briefly touched on outcomes and finished with some thoughts on the urgent need for restoration. From these comments, it should have been clear that I do not endorse the petition. I avoided providing an explanation for my opposition but, given recent commentary on discussion lists and superficial coverage in the press, in which the reporters consistently fail to ask the hard questions, I have decided to come forth with some thoughts on the petition and to suggest an alternative to the for/against positions that dominate current discourse on this issue.

OUR CHOICES

Our choices are based on the following three premises:

1) Monarchs are not threatened.

2) Monarchs are threatened.

3) Monarchs have declined due to habitat loss requiring large-scale funding of public-private partnerships (P3) to restore enough habitat to sustain the migration.

The potential outcomes associated with each premise are as follows.

1) Premise: Monarchs are not threatened.

We can argue that threatened status is not needed since there is enough milkweed left in the upper Midwest to produce an overwintering population of 3-4 hectares (Pleasants, pers. com.). We can also argue that the rebound in the population this year (from 33.5 million in 2014 to 56.5 million in 2015), indicates that threatened status and regulation are not needed at this time.

This position fails to recognize that milkweed/monarch habitat is declining at a rate of at least a million acres a year within the core breeding areas from Texas through the Upper Midwest (see Monarch Butterfly Recovery Plan).

Outcomes:
A) Monarchs will continue to decline

B) The public will eventually lose interest in monarchs (out of sight out of mind) and the migration will become a memory.

2) Premise: Monarchs are threatened.

Plan A: Threatened status implements standard rules and regulations.

We can argue that the evidence summarized in the petition justifies classification of the monarch butterfly as a threatened species. If the evidence is sufficient and the premise is accepted, threatened status will come with lots of rules, regulations and interpretations. There are rules and regulations that apply to critical habitat on public and private lands and regulations that restrict the public’s access to the species or habitats in question. Many are asking the questions, “How will monarchs actually be protected by such a ruling? What will be the impact on landowners, citizen science programs, backyard rearing programs, collecting, commercial breeding and distribution of monarchs? (See definition of “taking” in footnote.) Will the federal government have the personnel and funds (100s of millions of dollars) to enforce restrictions and administer a habitat program that covers much of the United States?” Threatened status for the monarch will have consequences and these need to be carefully considered. It is important for all concerned to be aware of the impact threatened status might have on their relationship with monarchs.

Outcomes:
A) Habitat protection and restoration will occur on both public and private lands and (i) lead to an increase in monarch numbers and a sustained migration or (ii) the scale of such efforts will be insufficient to protect the monarch migration

B) Milkweeds will be eradicated en masse on private lands before implementation of rules governing protection of milkweeds

C) Public interest in monarchs will decline following regulations restricting access to this species

D) Perceptions that the government will solve the “monarch problem” will diminish the public’s interest in creating habitats for monarchs

E) Constraints, particularly funding and personnel, will limit the prospect of saving the monarch migration

Plan B: Threatened status does not regulate critical habitat on private lands yet implements restoration partnerships with landowners.

Again, the presumption is that monarchs are threatened. In this case however, in recognition of the enormous task of tracking and monitoring milkweed/monarch habitats on private lands, and limited financial resources, attempts to protect critical milkweed habitats will be limited to public lands. Restoration of milkweed/monarch habitats on private lands will be accomplished through partnerships with landowners. Rules and regulations restricting public access to monarchs would still be implemented. Adoption of this approach also raises questions because the ability to form partnerships to restore habitat is likely to be constrained by various capacity issues such as funding and personnel.

Outcomes:
A) Habitat protection and restoration by federal agencies will be implemented on public and private lands but will be limited by the ability to engage landowners in milkweed/monarch conservation. Given the lack of protection of critical habitats on private lands, the scale of such efforts would be less likely to protect the monarch migration

B) Public interest in monarchs will decline following regulations restricting access to this species

C) Constraints, particularly funding and personnel, will limit the prospect of saving the monarch migration.

3) Premise: Monarchs have declined due to habitat loss requiring large-scale funding of public-private partnerships (P3) to restore enough habitat to sustain the migration.

Implementing threatened status under the Endangered Species Act will hinder rather than assure survival of the monarch migration.

We can also argue, given that the monarch population is likely to continue declining in the coming years, the best way to restore milkweed/monarch habitats is through large-scale public-private partnerships (P3) – collaborative efforts rather than those driven by regulations. This approach emphasizes that what we need are programs that foster cooperation and restoration on both public and private lands. Implied in the premise is the notion that milkweed/monarch restoration needs to start immediately and that we can’t wait for a decision on the petition. The petition puts us in limbo since the earliest a decision would be made is in two years and a determination of its merits could be deferred for a number of years.

Outcomes:
A) Habitat protection and restoration will occur on both public and private lands and (i) lead to an increase in monarchs numbers and a sustained migration or (ii) the scale of such efforts will be insufficient to protect the monarch migration

B) Beginning this season, an emphasis on grass-roots and large-scale campaigns will engage the public and feed into and facilitate large-scale habitat restoration

C) These programs will increase the number of citizens and private entities engaged in monarch conservation and conservation in general

D) The scale of this approach is more likely to lead to a larger and more stable monarch population than either plan 2A or 2B above.

Reasons for supporting choice 3 (P3) vs. plan 2A include the following:

1) The magnitude of the task is enormous and will create financial, management and personnel issues for already underfunded and understaffed agencies charged with protecting monarchs.

2) Restoration of milkweed/monarch habitat will cost hundreds of millions of dollars. Funding a federal effort of this scale would require a substantial increase in the endangered species budget or reallocation of existing funds away from other endangered and threatened species endeavors to cover costs associated with monarch recovery. Given the present economy and political climate, it seems unlikely that congress will provide funds to cover the costs associated with milkweed/monarch restoration.

3) Landowners are very concerned about programs wherein government regulations dictate how they manage their lands. (Plan 2B would involve willing landowners, thus bypassing this concern).

4) Threatened status represents a governmental top-down approach to a conservation program and gives the impression that “protection” will be achieved by government actions alone.

5) Choice 3 is inclusive and recognizes that saving the monarch migration will require broad-based public (government) and private actions. This choice recognizes that monarch conservation is too big a task for either the public or private sector acting alone.

6) Collaboration is the only reasonable solution given the magnitude, cost and complexities associated with monarch conservation.

7) Choice 3 provides a better path for getting landowners and stakeholders to participate in monarch conservation. In particular, we need to engage the landowners (farmers and ranchers) and rural communities throughout the Upper Midwest (the source area for most monarchs that overwinter in Mexico) in monarch conservation. At the same time, we have to be sure that landowners in Texas maintain milkweeds that support the offspring of monarchs returning from Mexico each March and April.

8) There is uncertainty as to whether the petition will be acted on favorably in the near term or delayed for a decade or more. Monarchs can’t wait for this decision or implementation of an action plan such as plans 2A or 2B. We have to act now and we have to build the coalitions, partnerships, capacity, etc., to assure that the monarch migration continues. Large-scale restoration needs to begin this spring.

Although I favor Choice 3, the success of this approach, just as with 2A and 2B, would depend on the scale of the effort to protect and restore milkweed/monarch habitats. Sustaining the monarch migration will not be easy. Here is one example of a large-scale public-private partnership currently under development: USDA News Release – Farm Bill Initiative Marks New Era for Conservation efforts

Throughout this text I have focused on issues associated with restoration on public and private lands. Rules and regulations that limit access to monarchs are another concern but how these might be implemented is still an open question. Readers who are concerned about how such rules might affect them should read the petition carefully (Petition to protect the monarch butterfly (Danaus plexippus plexippus) under the Endangered Species Act) and should submit comments accordingly (via eRulemaking Docket ID: FWS-R3-ES-2014-0056). Depending on what rules and regulations are adopted from the petition, or perhaps new ones suggested by an advisory committee, it is possible that many activities associated with monarchs would be prohibited or severely limited. It is also possible that some of the restrictions suggested in the petition would not be adopted. Restrictions are usually adopted to “protect” a species and the number of individuals in the population but, truthfully, in this case, due to the size and distribution of the monarch population and its reproductive capacity, adoption of such restrictions will have little impact on the size of the migration or the overwintering population. This issue is all about scale and biology and the question is whether human activities such as backyard breeding, commercial activities, etc., are of sufficient scope and scale to impact an abundant and highly mobile species with a high reproductive rate. The decision makers should carefully consider the strength of the scientific evidence apart from the rhetoric on these issues.

The following are some of the questions that have concerned me about the petition. In addition to these questions, for which there are presently few answers, my preference for public-private partnerships, rather than threatened status, is based on participation in a number of high level meetings with scientists, experts from federal agencies, conversations with representatives of various NGOs and persons representing agricultural interests and industry. My sense is that monarch conservation is moving in the direction of public-private partnerships – irrespective of the petition requesting threatened status for the monarch.

Questions relevant to the petition

General questions

What is meant by the word “protection” in the context of protecting the monarch migration?

What would be protected and how would specific actions protect monarchs?

If the government is required by the Endangered Species Act to restore habitats for monarchs, what would be involved?

Assuming that the goal is to protect critical habitat, how do we define critical habitat?

Assuming we can identify and protect critical habitat on public lands, what would that mean for private lands?

How much land needs to be restored each year to compensate for the annual losses of milkweed/monarch habitats due to development, increase in crop acreage and other forms of land degradation? (Annual losses in the milkweed/monarch corridor are estimated to be at least a million acres per year – see Monarch Butterfly Recovery Plan).

How much land would have to be restored to bring the monarch back to a more stable population size – i.e., a population large enough to be able to survive catastrophic overwintering mortality and poor breeding seasons? Since most of these annual losses occur on private lands, how could threatened status be used to restore milkweeds to these or comparable sites? Who would monitor the habitat losses and who would follow up with appropriate remediation? How would this be coordinated and how would it be paid for?

How much does it cost to restore an acre of milkweed/monarch habitat? Depending on the method, costs of restoration and maintenance of milkweeds and nectar plants range from $100-$1000 per acre. If we need to compensate for the loss of a million acres per year in the milkweed/monarch corridor, the restoration alone could cost 100 million dollars per year and there would be additional millions associated with administrative costs as well. Who would cover those costs, especially if most of the restoration occurred on private lands? And, again, what sort of incentives and agreements would be needed between the government and landowners to accomplish this restoration? Further, do we have the capacity (e.g., seed stocks) for large-scale restoration and who would do it – federal, state or private restoration teams?

Going beyond the 1 million acres per year, how would the restoration of additional millions of acres be accomplished? And, how many millions are we talking about? Estimates are that 167 million acres of milkweed/monarch habitat have been lost since the introduction of GMO crops in 1997 and the signing of the ethanol mandate in late 2007. How much habitat needs to be restored to offset enough of this loss to create a population of sufficient size (4-5 hectare overwintering population) to be able to sustain losses due to extreme weather at the overwintering sites, or temperatures during March and April in the South Region (TX, OK and southern KS), or during extreme cold or warm summers in the Upper Midwest? Do we need to restore 5, 10 or 15 million acres? And, again, at what cost and who is going to do it and how much would involve public vs. private lands? Aside from capacity issues (seeds, manpower, equipment, etc.) would the federal government have the personnel, the infrastructure and the 100s of millions of dollars necessary to achieve the levels of restoration needed to sustain the monarch population?

Questions based on the assumption that plan 2A would be adopted

Would developers be blocked from developing due to the presence of milkweeds on properties they would like to develop? The rate of conversion of landscapes to development (housing, malls, industrial parks, etc.) is approximately 2 million acres per year – of which 1.24 million acres are rural lands (Farmland Information Center statistics).

If development involved displacement of milkweeds, would the developer be required to restore milkweeds in new areas? Who would coordinate these arrangements?

What types of incentives and agreements would be needed to get private land-owners to restore milkweeds and nectar plants to their properties?

How would existing milkweed stands on private lands be identified within the northern breeding area and throughout the milkweed/monarch corridor from Texas to the border with Canada. And, once identified, how would milkweed sites on private lands be protected? Would there be penalties for not properly maintaining milkweed patches on private land or purposefully destroying such patches?

Questions based on the assumption that plan 2B would be adopted

Plan 2B would be much like Choice 3 but would include various but, as yet undetermined, restrictions on the public’s access to monarchs. At issue here is the question about the size of the Federal effort. Would federal agencies have sufficient funds and personnel to cover a significant portion of the costs needed to restore the monarch population? This question takes us back to the magnitude of the effort needed to restore the monarch population. Habitat for monarchs is critically low. There is no excess habitat. The monarch population will continue to decline if we fail to recognize the annual rate of habitat loss (a million acres/year) and to offset these losses with restoration.

What’s the best plan for saving the monarch migration?

Which of the choices above gives us the best chance of saving the monarch migration? My money is on Choice 3 – public-private partnerships (P3). However, for this effort to be successful, we need a multitude of large-scale public-private partnerships that focus on the restoration of milkweed/monarch habitats from the Upper Midwest through central Texas. Further, we need to enhance monarch habitats throughout the United States.

There are many other questions and numerous long-term issues that neither the petition nor these comments address. That said, the most important question is – how can we slow down and even reverse the decline in monarch numbers? Given that we are losing at least a million acres of critical habitat a year, we can’t wait for a decision on the petition. We have to act NOW!

Definitions from the Endangered Species Act of 1973

The term “threatened species” means any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.

The term “endangered species” means any species which is in danger of extinction throughout all or a significant portion of its range.

The term “take” means to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.

(5)(A) The term “critical habitat” for a threatened or endangered species means—
(i) the specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the provisions of section 4 of this Act, on which are found those physical or biological features (I) essential to the conservation of the species and (II) which may require special management considerations or protection; and
(ii) specific areas outside the geographical area occupied by the species at the time it is listed in accordance with the provisions of section 4 of this Act, upon a determination by the Secretary that such areas are essential for the conservation of the species.
(B) Critical habitat may be established for those species now listed as threatened or endangered species for which no critical habitat has heretofore been established as set forth in subparagraph (A) of this paragraph.
(C) Except in those circumstances determined by the Secretary, critical habitat shall not include the entire geographical area which can be occupied by the threatened or endangered species.

Monarch Population Status

World Wildlife Mexico in collaboration with SEMARNAT and CONANP and the Monarch Butterfly Biosphere Reserve (MBBR) announced the total forest area occupied by overwintering monarch colonies early this morning in Mexico City. Nine colonies were located this winter season with a total area of 1.13 hectares. Although this figure represents an improvement from the 0.67 hectares recorded last year, it’s the second lowest population on record and the third low population in as many years. Populations of this size are extremely vulnerable. Winter storms or poor conditions for breeding in the spring and summer could have a severe impact on a population of this size. If there are no winter storms in the next three weeks and conditions are favorable as the monarchs move northward in March to Texas, the long range forecasts suggest that the population has a good chance of increasing again next year.

Figure 1. Total Area Occupied by Monarch Colonies at Overwintering Sites in Mexico

We will provide additional details as we receive and process them – in the meantime, the official press release (in Spanish) is available to view/download here: COMUNICADO-MARIPOSA-MONARCA-2015.pdf

Monarch Population Status: Addendum

As an addendum to our Monarch Population Status report posted on 29 July 2014, I offer the following:

Reports from throughout the breeding range indicate an increase in monarch numbers roughly along the lines projected in May. The migration is already underway having started at 50 N around the 12th of August. The leading edge should be in southern MN at this time and in Ames, IA around the 6th of Sept. Fall roosts have been reported to Journey North in the Dakotas, MN, WI, MI and NY as of 28 August. No roosts had been recorded by the 29th of August last year (see Monarch Roosts Fall 2013 and Monarch Roosts Fall 2014). There will surely be more monarchs to tag over the next two months and the overwintering population in Mexico is certain to be larger. At a minimum, I expect the population to be twice as large as last year or roughly 1.4 hectares but it could be twice that size. We still have to hear about monarchs from many areas and the conditions during the migration will likely determine how many of the migrants reach the overwintering sites. It will help to watch the reports of overnight clusters recorded by Journey North and to watch the weather conditions and note the availability of nectar sources as monarchs migrate through the United States and northern Mexico.

Commentary: Recent Petition to Protect the Monarch Butterfly

On August 26th 2014, The Center for Biological Diversity, Center for Food Safety, The Xerces Society, and Dr. Lincoln Brower submitted a petition to the Secretary of the Interior and the Fish and Wildlife Service requesting that the monarch butterfly be granted threatened status under the provisions of the Endangered Species Act. The petition is quite thorough (159 pages) and details evidence of the decline in monarch numbers, the numerous causes for the decline and the large number of threats to the population due to natural (parasites and predators) and human related causes ranging from pesticides to climate change. It’s an excellent summary of information those of us interested in monarchs should be familiar with. The full petition can be found at xerces.org/wp-content/uploads/2014/08/monarch-esa-petition.pdf

The petition has generated a great deal of discussion via social media, our discussion list (Dplex-L) and among groups as diverse as collectors, amateur butterfly enthusiasts and commercial butterfly breeders. There is a great deal of concern as to how threatened status would affect how we all interact with monarchs whether it would be through collecting, rearing, tagging or various forms of monitoring. These concerns are heightened by the presumption that a decision on this petition could happen soon. Further, there is some confusion about the terminology and process involved in designating a species as endangered or threatened.

The following paragraphs are intended to help clarify some of the issues associated with the petition.

Terminology
We need to be clear on the terminology.

“An ‘endangered species’ is one that is in danger of extinction throughout all or a significant portion of its range. A ‘threatened species’ is one that is likely to become endangered in the foreseeable future throughout all or a significant portion of its range.” (fws.gov/endangered/esa-library/pdf/listing.pdf).

Monarchs clearly aren’t endangered. This petition requests threatened status for the monarch based on the presumption that the monarch migration is threatened due to the loss of a significant portion of its breeding range in the upper Midwest, i.e. the corn belt. But, is it? That’s a matter of evidence and interpretation. As this discussion proceeds, we need to make it clear in all communications that it’s about the migration and not the species per se.

Process
The Fish and Wildlife Service has 90 days to respond to the petition. It’s likely they will accept the petition for further evaluation and will set a date for a public comment period that will start in about 15 months. This will be followed by further evaluation, perhaps requests for additional data, etc. Most of these petitions require lengthy reviews and revisions. Due to the large number of petitions for threatened and endangered status for a wide range of plants and animals, the significant number of high priority cases under consideration and personnel limitations at Fish and Wildlife, it could be many years, 5 at a minimum, possibly 10 or more, unless the monarch decline accelerates, before a determination is made as to whether monarchs are deserving of threatened status.

A schematic of the process can be found at fws.gov/endangered/what-we-do/listing-petition-process.html

A key statement is the following:
“A positive one-year finding can be incorporated into a proposed listing or, if a prompt proposal is precluded by other listing activities, the proposal may be deferred. These ‘warranted but precluded’ proposals require subsequent one-year findings on each succeeding anniversary of the petition until either a proposal is undertaken or a ‘not warranted’ finding is made.”

My understanding is that most proposals of this type are repeatedly deferred – some for as long as 20 years.

Outcomes
Petitions of this sort can have both positive and negative consequences. On the positive side, they tend to rally the advocates, draw broader attention to real conservation problems and attract funding that can help mitigate the problem. On the other hand, private landowners and other groups that have an interest in the status quo often challenge such proposed conservation measures. The fear of regulation, or the possibility of the government telling landowners what they can and can’t do with their land, rallies the opposition. This polarization can become political. There are a number of ongoing battles along these lines. Monarch conservation needs to remain apolitical and will be best served if we engage landowners rather than drive them away. The petition ends with a request for critical habitat designation (p 113). With statements such as “‘Of equal or more importance is the determination of the habitat necessary for that species’ continued existence… If the protection of endangered and threatened species depends in large measure on the preservation of the species’ habitat, then the ultimate effectiveness of the Endangered Species Act will depend on the designation of critical habitat.’ H. Rep. No. 94-887 at 3 (1976).” But nowhere in this section, or elsewhere, is it clear what critical habitat means in the case of monarch butterflies or how it might be designated and protected. Designations of critical habitat will have to be carefully crafted to avoid a backlash from landowners.

Habitat restoration
It is clear, as we have pointed out many times, that the monarch population is in decline due to loss of habitat. The petition is all about protection and covers habitat loss in great detail. However, protection alone will not stop the decline in monarch numbers. Unless we collectively address the annual loss of habitat with a significant recovery plan that restores at least 1-1.5 million acres of milkweed/monarch habitat per year – the eastern monarch migration will dwindle further to the point where it will be truly threatened. It’s been evident for some time that, petition or not, we have to restore habitats for monarchs. (monarchwatch.org/blog/2014/03/monarch-butterfly-recovery-plan/).

Monarch Watch is engaged with a large number of colleagues in discussions about how to provide more habitat for monarchs. The White House supports these initiatives through the Presidential Memorandum of 20 June. We are making progress with these discussions, and the goal is to implement broader conservation measures by next spring. If we (the monarch community in general) can create the needed partnerships and collaborations and obtain significant funding, the monarch migration can be saved. Saving the monarch migration is one of the easier conservation challenges we face. Let’s do it!

Monarch Population Status

Those of you who follow monarchs closely are aware that the monarch population has been declining for the last 10 years with significant drops in the population each of the last three years. The number of trees and total area occupied by monarchs in the oyamel fir forests in Mexico was at an all time low last winter – a mere 0.67 hectares. This decline has given rise to a great deal of concern about the future of the monarch migration. These concerns have resulted in many meetings and plans, and even a Presidential Memorandum directing federal agencies to devote resources to offset the decline in monarchs and pollinators. We have addressed this issue through our Monarch Waystation, Bring Back the Monarchs and Milkweed Market programs. These programs are growing but they need to become much, much larger to sustain the monarch migration. Large-scale habitat restoration, particularly in the upper Midwest, also needs to become a priority. In the meantime, we need to keep tagging monarchs as a way of monitoring their numbers and tracking any shifts in the origins of monarchs that reach Mexico. If you are a long-term tagger, you know it has been increasingly difficult to find enough monarchs to tag, especially during the last two years. The totals tagged each year roughly parallel the numbers recorded in Mexico each winter, giving us an independent assessment of the numbers in the migration. Regional tagging success also helps in that it demonstrates how monarchs respond to the physical conditions and quality of the habitats in these areas. Thus, tagging is an important tool to help us understand the overall dynamics of the monarch population.

So what should we expect this year? I usually like to wait until August to make predictions about the numbers in the migration and avoid bold assertions about the size of the overwintering population until well into the migration. However, this year I’m on record as early as the 3rd of May on our discussion list Dplex-L as predicting that there will be a modest increase in the number of monarchs in the migration and at the overwintering sites this winter. “Modest increase” is a vague term and I can’t put a number to it; however, all of the factors I’ve researched indicate that there will be more monarchs migrating this fall and at the overwintering locations by mid December when the colonies are measured. All in all things are looking up for monarchs this year.

Here is a brief overview of factors supporting my prediction of a modest increase in the number of monarchs this fall:

1. I looked at reports from those visiting the overwintering sites about the mortality seen at the colony locations. I also watched the weather in Mexico to be sure that there were no unusual weather events at the overwintering sites that would contribute to mortality. Fortunately, though the population was low, it seemed to winter well.

2. I followed the first sightings reported to Journey North and monitored, as closely as I could, the conditions of the milkweed and flowering of nectar sources in Texas. Since lower than normal temperatures in Texas in March and early April are also associated with an increase in the population, I monitored the temperatures in the region as well. Again, all the signs pointed to a slight growth in the population.

3. The temperatures during May and early June are another key to population growth. These temperatures largely determine when the first generation monarchs coming out of Texas and Oklahoma will reach the northern breeding area. Past records have shown that the timing of arrival of these monarchs in the north (i.e., >40N) is also critical. First sightings suggested fair numbers arrived during the critical period in the upper Midwest, smaller numbers arrived later in MI, OH and ONT and, still later, even fewer reaching the New England area. All of which suggested that most of the increase would come from the upper Midwest assuming that summer temperatures were normal or above normal.

4. A look at the longer-term temperatures suggested that normal temperatures could be expected over most of the northern breeding area, further supporting my optimistic outlook through May and early June.

5. The reports so far this July have not been disappointing. The 4th of July butterfly counts supported by the North American Butterfly Association, and other counts, have generally reported better numbers of monarchs in their surveys than last year.

Good luck with your tagging and thanks to everyone that participates in our programs!

ADDENDUM: 2 September 2014

Reports from throughout the breeding range indicate an increase in monarch numbers roughly along the lines projected in May. The migration is already underway having started at 50 N around the 12th of August. The leading edge should be in southern MN at this time and in Ames, IA around the 6th of Sept. Fall roosts have been reported to Journey North in the Dakotas, MN, WI, MI and NY as of 28 August. No roosts had been recorded by the 29th of August last year (see Monarch Roosts Fall 2013 and Monarch Roosts Fall 2014). There will surely be more monarchs to tag over the next two months and the overwintering population in Mexico is certain to be larger. At a minimum, I expect the population to be twice as large as last year or roughly 1.4 hectares but it could be twice that size. We still have to hear about monarchs from many areas and the conditions during the migration will likely determine how many of the migrants reach the overwintering sites. It will help to watch the reports of overnight clusters recorded by Journey North and to watch the weather conditions and note the availability of nectar sources as monarchs migrate through the United States and northern Mexico.

Milkweed inventory – plants remaining

Although we have been shipping milkweeds like crazy – about 30K so far – we still have a few – actually quite a few (22K)- plugs left that are well rooted and ready to ship. We need to find homes for these plants. The attached spread sheet shows the ecoregions from which the seeds originated and to which we will send the plants. We use the Bailey Ecoregions as a guide. We have been advised to use these ecoregions to return plants to the zones to which they are best adapted. When we can, we return the plants to the same state as the seeds originated from though the ecoregion may span several states – e.g. 251.

Please pass this around. Due to a number of miscalculations and just the shear confusion of trying to keep track of the successful production from 112 different seed lots – which in most cases was higher than anticipated, we ended up with more plugs than we expected.

Thanks for any help you can provide. The flats with plugs (N=32) are available for $60.80 each through the Milkweed Market. Shipping is included for most locations but we are finding it necsssary to expedite the shipping (with associated higher costs) to areas where the temperatures are above 90F at this time of year. (Heat damaged plants aren’t pretty).

If you are interested in plants from California, A fascicularis is still available. Again, please send an email to milkweed@monarchwatch.org indicating your interest in these plants.

For additional information please visit our Milkweed Market

Monarch Butterfly Recovery Plan

The following is a memo outlining a recovery plan for monarch butterflies. On 1 March I received an email from a person well connected with monarchs asking me to prepare a document, a prospectus or memo, for business leaders by the end of the day. I was told that these persons needed background information about the monarch population along with a rough idea of what would be required to address the loss of milkweed/monarch habitat. The memo was prepared in haste and is not inclusive of all the components needed to successfully stabilize and then increase the milkweed habitats that support the monarch population. Nevertheless, this document outlines some of the basic issues. Hopefully these ideas will be useful in shaping the conversations needed to create a vision and plan as to how best to restore the monarch population. The original memo has been rewritten to improve clarity. An explanation of the estimated annual loss of habitat has been added as well.

Introduction
The following text is a brief summary of the status of the monarch butterfly population. The reasons for the rapid decline in monarch numbers are discussed along with a proposed recovery plan. Recovery will be possible if 1) plans can be implemented to offset the annual losses of milkweed due to development and the expansion of croplands and 2) significant efforts are made to maintain the milkweed corridor that sustains the vast majority of monarchs that reach the overwintering sites in Mexico.

A declining population
The number of hectares of forest occupied by overwintering monarch populations in the Monarch Butterfly Biosphere Reserve (and neighboring sites) in Mexico is shown in Figure 1 below. The forest area occupied by monarchs for 2013-2014 is the lowest recorded to date and continues the progression toward smaller winter numbers seen over the last decade. The decline has been attributed to three main factors: 1) the widespread adoption of herbicide tolerant corn and soybean varieties by North American farmers which has had the effect of eliminating milkweeds (the host plants for monarchs) within the crop fields; 2) the ethanol mandate passed by Congress in 2007 that increased the price of corn and soybeans which in turn led to the conversion of grasslands to crops thus elimination of the milkweeds that occurred in these areas; and 3) three consecutive years during which the reproductive success of the summer breeding population was limited by unfavorable weather conditions. The loss of habitat, i.e. milkweed and nectar plants that sustain the monarch population, is massive yet can be mitigated. In the paragraphs below I will briefly outline a vision and goals for monarch recovery and will describe the infrastructure, resources and partnerships needed to implement this recovery plan.

Figure 1. Total area occupied by monarch colonies at overwintering sites in Mexico.

Spring and summer breeding
Although monarchs can be found throughout the United States and southern Canada in the summer months, the main part of the population utilizes two critical areas with milkweeds: 1) the spring breeding area shown in Figure 2 below which encompasses most of Texas, Oklahoma, and part of Arkansas and Kansas; and 2) the upper Midwest (the eastern Dakotas, Minnesota, Wisconsin, Iowa, Illinois, Michigan and parts of Indiana). Monarchs arriving in the southern area from Mexico (in March) lay eggs on milkweeds, and the adults that develop as a result of this reproduction move northward into the summer breeding range in May and early June. This northward moving first generation spreads out over the north from the Dakotas to the Maritime Provinces in Canada. However, it is the production of the monarchs in the center of the “corn belt” that is critical. Our tagging data over the last 20 years and an earlier study using isotopes (Hobson and Wassenaar 1998, Wassenaar, et al. 1999) have shown that most of the monarchs reaching the overwintering locations in Mexico originate from this region.

Figure 2. Spring and summer breeding areas in the milkweed/monarch corridor in relation to corn acreage planted in 2011.

The milkweed/monarch corridor
These two important areas of reproduction constitute what I call the milkweed/monarch corridor. Unfortunately, it is within this corridor that a large portion of the milkweed-containing habitat has been eliminated (Figure 3). Loss of habitat in this region is likely to continue which will lead to a further decline in monarch numbers.

Figure 3. Areas of grasslands, shrub lands and wetlands converted to croplands 2008-2011. Increases in acreage by crop type are shown at the bottom of the figure. From Faber, et al. 2012.

Premise
The monarch population will continue to decline unless 1) the annual loss of habitat (.5 to 1.5 million acres**), due to conversion of landscapes to crops and development, is addressed and 2) large-scale restoration of milkweeds is initiated to offset the losses of habitat that have occurred over the last 15 years.

Vision and goals
The monarch migration can be saved if there is commitment to the two propositions outlined in the premise to 1) offset annual losses of habitat by planting milkweeds and nectar plants in areas from which they have been extirpated and 2) develop the capacity to plant milkweeds over large landscapes. Both projects require the development of greater capacity to restore milkweeds than exists at present.

Implementation
Implementation of this recovery plan will depend upon the development of many different components. The program will require: 1) marketing and outreach so as to engage citizens, agencies, corporations, institutions and farmers; 2) a means of identifying landscapes on which milkweeds can be restored such as Conservation Reserve Program (CRP) lands, private lands, roadsides, federal lands, state and local parks, marginal landscapes, corporate landscapes and buffer strips; 3) a program to develop partners who can contribute to the success of the program such as nurseries, seed growers and native plant societies; 4) participants who can help with the seed collecting and plantings such as children in 4H programs, Future Farmers of America (FFA), Scouts, schools and other environmental organizations; and 5) communications with Federal, State and Local authorities to facilitate these efforts.

Capacity building and time frame and costs
In my view, the capacity to offset annual losses of milkweed/monarch habitat doesn’t exist at this time. The production of milkweed seeds and plugs (small plants) needs to increase rapidly. In addition, outreach needs to be developed and partnerships formed to get the seeds and plugs planted. By moving rapidly to implement this plan, the means to offset annual habitat losses can be developed in three years, and by the fourth year it should be possible to address the habitat losses that have accumulated over the last 15 years. Offsetting the annual habitat loss will require the establishment of at least 5-15 million milkweeds via the planting of seeds and plugs. Given the need to develop the infrastructure – seed production, etc., mentioned above, my estimate is that the yearly budget for this program should be $xxxxx million***. If more funds are available, the project could be expedited.

*This memo details what might be done to restore the monarch population that breeds east of the Rocky Mountains.

**Annual loss of habitat. One result of the ethanol mandate of 2007 has been the conversion of 24 million acres of grassland, rangeland, wetlands and shrub lands to crops. The loss by county for 2008-2011, 23,681 million acres, is shown in Figure 2. An additional 400,000 acres were converted to crops in 2012 bringing the total to more than 24 million acres. Figures for the conversion of grasslands (much of it retired CRP land) to croplands for 2013 are not yet available. Although the rate of conversion to croplands may be slowing down, Congress has mandated a further reduction in the CRP program with a cap at 24 million acres by 2017. The bottom line is that milkweed-containing habitats within the farming sector will continue to decline but – by how much? Annual losses of .5-1.5 million acres are likely but these estimates are based on a number of assumptions as follows:
1) Conversion of grassland and retired CRP lands to croplands will continue at rates of 350-450 thousand acres per year.
2) Loss of habitat due to development will continue. The annual conversion of landscapes in the United States to building sites and the expansion of cities is in excess of 2 million acres per year. Much of this development, perhaps 500,000 acres, occurs in the monarch summer breeding range. Other losses, perhaps 100,000 acres per year, are occurring in monarchs’ spring breeding range.
3) Losses outside the corridor will continue and these losses will also have a negative impact on monarch numbers.
4) There are additional losses of milkweed/monarch habitats that are not easily accounted for such as land management decisions that eliminate milkweeds and other forbs from pasturelands, roadsides and other land parcels.
5) Lastly, this interpretation assumes that the price of corn will remain in the $4-$5/bu range. Higher prices are likely to result in the conversion of more milkweed containing habitats to croplands.

It should be clear that, although the figures for the annual loss of milkweed/monarch habitat are not firm, it is likely that these losses will be close to a million acres per year for the foreseeable future.

***I have not prepared budget for this project. As you can see from the above, capacity building and implementation are both complicated and will require a major effort from many participants. Suffice to say, the annual cost of this program will be many millions. The project needs to be refined more precisely before dollar figures can be assigned to the different cost centers.

References

Cropland conversion. 2014.
http://www.fsa.usda.gov/FSA/webapp?area=newsroom&subject=landing&topic=foi-er-fri-dtc (accessed 28 January 2014).

Faber, Scott, Soren Rundquist and Tim Male. 2012. Plowed Under: How Crop Subsidies Contribute to Massive Habitat Losses. Environmental Working Group http://static.ewg.org/pdf/plowed_under.pdf (accessed 28 January 2014).

Hobson, Keith A., Leonard I. Wassenaar and Orley R. Taylor. 1999.
Stable isotopes (dD and d13C) are geographic indicators of natal origins of monarch butterflies in eastern North America. Oecologia (1999) 120:397±404.

Wassenaar LI, Hobson KA. 1998. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence. Proc Natl Acad Sci 95:15436±15439.

For further information about monarchs, milkweeds and Monarch Watch, please visit MonarchWatch.org.

Further commentary

Obviously, mitigating the decline in the monarch population will require a great deal of discussion. In the above I’ve only addressed what it might take to mitigate the annual losses of milkweed monarch habitat. The larger issue is how to restore sufficient habitat so that the overwintering monarch population will be large enough, and will survive in sufficient numbers to repopulate the milkweed/monarch corridor each year. There is a history of catastrophic mortality at the overwintering sites (70-80% losses due to winter storm in 2002 and 2004). The large overwintering populations of 2001-2002 (9.35ha) and 2003-2004 (11.12ha) survived in sufficient numbers to recover from these losses in two years. Overwintering populations of a hectare or less will not fare as well should they experience such mortality. The recovery would take much longer. How can the latter scenario be avoided? My interpretation is that – at a minimum – our larger target should be to provide sufficient milkweed/monarch habitat to sustain populations of 4 hectares or more from year to year. Even with high winter losses such populations should be robust enough to repopulate the United States in the spring.

There are more questions of course. What are the near and long term goals? How much will the project cost and where will the funds come from? Will public funds be available? Will corporations, foundations, environmental organizations and private individuals support this effort? How will the funds be administrated? Who are going to be the partners in this enterprise and who will take the lead in coordinating the implementation of this program?

There are lots of questions; monarchs need the answers.

Monarch Population Status

The overwintering numbers are in from Mexico and once again it’s bad news. The numbers are not a surprise; as early as May, we predicted that the population would be lower this winter. I’ll discuss our reasons for this expectation and the overall decline seen throughout the last decade, but first, let’s look at the numbers reported by World Wildlife Fund, Mexico.

Figure 1. Total Area Occupied by Monarch Colonies at Overwintering Sites in Mexico

Habitat Loss

In previous postings to this Blog I’ve mentioned three factors that have contributed significantly to the loss of monarch and pollinator habitats: the adoption of herbicide tolerant (HT) crops, the ethanol mandate, and development. In my lectures I’ve presented figures in which I try to quantify the loss of habitat attributable to each of these factors. The expected low numbers of monarchs in Mexico this winter have caused me to reevaluate and clarify these losses. My interpretation is summarized in the two tables below. The loss of monarch habitat due to the adoption of HT crops and the ethanol mandate is summarized in Table 1. The overall loss of monarch habitat is shown in Table 2.

Let’s deal with the HT crops first.

If you have been following postings to this Blog, you know that row crops (e.g., corn and soybeans) contained relatively small quantities of common milkweed when tillage was used to control weeds in these fields. Some milkweed survived and a survey conducted in 2000 (Oberhauser, et al 2000) showed this habitat to produce more monarchs per acre than other milkweed/monarch habitats. With the adoption of HT crop lines, the use of glyphosate has all but eliminated milkweeds from these habitats (Brower et al 2011, Brower et al 2012, Pleasants and Oberhauser 2012 and personal observations).

One of the startling aspects of the corn and soy dynamics is the increase in acreage over the last 17 years. In 1996 the total acreage for corn and soy was 143.5 million acres while in 2013 was 174.4 million acres – an increase of 29.5 million acres. Note that while the acreage increased by 9.5 million acres from 1996 to 2006, the acreage increased by 20 million over the last 7 years. This increase is largely due to the ethanol mandate. Early in 2007 congress passed the Clean Energy Act of 2007, frequently referred to as the ethanol mandate. It was apparent to many growers in the spring of 2007 that this act was going to increase the demand for and price of corn. Corn planting has been increasing ever since with the result that farmers have removed hedgerows and narrowed field margins. In much of the corn-belt, farming is from road to road with little habitat for any form of wildlife remaining. Grasslands – including some of the last remaining native prairies, rangelands, wetlands, and 11.2 million acres of Conservation Reserve Program (CRP) land – have been plowed under to produce more corn and soybeans. Most of these acres formerly contained milkweeds, monarchs, pollinators and other forms of wildlife. They are gone and the total loss of these habitats since 2008 exceeds 24 million acres (an area about equal to the state of Indiana).

Development consumes about a million acres of farmland a year and the conversion of woodlands and other landscapes to shopping malls, housing and roadways consumes another million acres a year. Overall, the loss of various habitats due to development probably exceeded 34 million acres since 1996. Some of this habitat was in the West and since we are just considering the eastern monarch population, I’m estimating the total loss due to development to be 17 million acres. Not all of these landscapes contained milkweeds but much of it did at one time. There are also habitat losses due to excessive mowing and use of herbicides along roadsides. In an earlier study (Taylor and Shields 2000) we showed that the area from the edge of the road to the edge of the field was about 1% of the total land area in most eastern states. These were significant milkweed and monarch habitats in the past but it appears that much of this habitat has been lost as well due to these practices. Unfortunately, there is no way to estimate this loss.

I’ve summarized the total loss of habitat in Table 2.

My conclusion is that at least 167 million acres of monarch habitat has been lost since 1996. Not all of the corn and soybean acreage occurs within the summer breeding range for monarchs so the total loss of monarch habitat due to HT crops is lower (150 million) than the total area (174.5 million) planted in 2013. The 24 million acres of grasslands, etc. converted to croplands since 2008 have been included in the estimated loss to HT crops. Add to this number the estimated loss due to development and the total is 167 million acres lost but this could easily be an underestimate since there are losses such as roadside management that we can’t account for. To give you some perspective on the area that is represented by this figure, consider the following: 167 million acres =261 thousand square miles – an area just below the total acreage of MN, WI, IA and Il (266 thousand square miles) and Texas (266 thousand square miles).

The total summer breeding range for monarchs is probably 800-900 thousand square miles. If it is true that 261 thousand square miles of this range no longer contains milkweeds and nectar plants for monarchs, it would mean that 29-33% of the monarch breeding range has been lost. This loss is calculated based on the entire summer breeding range. A more refined approach confined to the states and the region of southern Ontario that produce most of the monarchs that reach Mexico is likely to show that the loss in these areas is much higher. Have I overestimated these losses? Maybe – but probably not. In any case, due to the economic forces involving crop production and human population growth, these losses will continue. It is clear that if our goal is to save the monarch migration, we must find a way to mitigate the loss of monarch habitat.

Reproductive Success

In a long article posted to the Blog on the 29th of May 2013 (“Population Status“), I discussed the prospects for the development of the monarch population over the coming months. The article started as follows:

“Monarchs are off to a slow start this year, with the number moving north in May at an all time low (as indicated by first sightings reported to Journey North). In the following paragraphs I’ll explain why this will be a lean year for monarchs and why the overwintering population in Mexico could be even lower this coming winter than it was in 2012-2013. Predicting whether monarch populations will increase or decrease would seem to be risky or even foolish but, as you will see, there are patterns that support these predictions based on: 1) overwintering numbers; 2) first sightings in the spring (1997-2013); and 3) the impact of temperature on the development of the first generation immature stages and the ability of adult monarchs to move northward to recolonize the breeding areas in the northern states and Canada.”

The above was followed by a long explanation of the patterns of first sightings and comparisons of the numbers of first sightings and temperatures during the breeding season for other low years. I concluded with the following summary:

“So, what does this tell us about what to expect in the fall and winter of 2013? Let’s deal with the number of observations first. Although, the number of first sightings reported in 2013 is similar to those of 2004 and 2005, the number of people reporting first sightings has increased significantly since reporting of first sighting began in 1997 (Howard and Davis 2004). In other words, fewer monarchs have been seen this year by a larger group of observers – suggesting that the number of returning monarchs was lower in 2013 than in 2004 and 2005 (both low returning populations) or even 2010, which saw the lowest overwintering population (1.92 hectares) prior to that of this past winter.

There is a similarity between 2013 and 2004 – the monarchs will arrive late in the northern breeding areas. The mean temperatures for March (-2.0F) and April (-2.7F) were the lowest for these months since 1996 and the April temperatures in particular slowed development of immature stages. May temperatures – which in most of the South Region are near or just below normal – have not appreciably aided northward movement of first generation monarchs. The result of all of these factors is that the arriving number of first generation monarchs will be low and they will arrive late. Even if this projection is true, is there a chance that the population can rebound as it did in 2005? Yes, but the temperatures in nearly all of the northern breeding range will have to be above normal by 2-3F throughout the summer for the population to increase. If the temperatures are normal (and normal summer temperatures are projected by NOAA for the upper Midwest (see the National Weather Service’s Climate Prediction Center), the overwintering population is likely to be in the range of 1 hectare again this coming winter and could be much lower.”

As it turned out – all of the above came true. The monarchs did arrive late in the summer breeding areas. The number of arriving butterflies was also low. In the northeast temperatures favored nearly on time arrival of the colonizing butterflies but extensive periods of cool, rainy days limited reproductive success. The conditions were so poor for reproduction in the northeast that it became clear in August that the number of monarchs that would be recorded at Cape May, New Jersey, during the migration would be quite low and it was (third lowest recorded since 1992). NOAA was right on target with the temperature predictions too. Normal temperatures were experienced throughout the northern areas – not the higher than normal temperatures that were needed to increase the population. The delayed arrivals apparently resulted in a late migration at the end of the season. Throughout the fall we kept hearing how late the migration was. In Lawrence, KS we had some on time arrivals, a rather small number, followed by a bit of a delay and then a flush of late migrants. In a year with an early onset of freezing weather many of these migrants would not have survived. But it was a warm fall and they kept moving, arriving later than usual in the vicinity of the overwintering sites in Mexico.

Every year is unique but some years deviate more than others from the norm. 2012 and 2013 both deviated from normal with 2012 being too hot and 2013 being too cold at critical times, and both resulted in low overwintering numbers. We break the breeding season into three intervals: March-April, May- 9 June, and June-August. The temperatures in 2012 were higher in each of these intervals than for any of the last 18 years. In 2013 the temperatures were lower than normal for the first two periods. However, it was the lower than normal temperatures in April that slowed development of immatures, and somewhat cooler May and early June that delayed the recolonization of the summer breeding areas.

Monarch numbers will rebound but only if the weather allows AND there is enough milkweed to increase the population. While we will never get back to the large populations of the 1990s, there is still enough milkweed to produce monarchs in sufficient numbers to colonize 3-4 hectares of the forests in Mexico. However, given the current size of the overwintering population it is likely that it will take 2-3 years with relatively favorable breeding conditions for the population to attain such numbers.

Looking ahead, NOAA is predicting higher than normal temperatures for Texas in March and April – which wouldn’t be good. On the other hand, some of the weather services are projecting normal temperatures through mid-March. That sounds better to me. Let’s hope there are favorable conditions for monarchs over the next several years. While waiting for conditions to improve, let’s plant milkweed – lots and lots of it.

I wish to thank Vijay Barve, Janis Lentz, Elizabeth Howard for help determining the patterns described above and to Jim Lovett for his assistance on the figures and formatting of this Blog entry.

References

Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zubieta, R.R. & Ramirez, M.I. (2011) Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conservation and Diversity, 5(2): 95-100.

BROWER, L. P., TAYLOR, O. R., WILLIAMS, E. H. (2012) Response to Davis: choosing relevant evidence to assess monarch population trends. Insect Conservation and Diversity (2012) 5, 327–329.

Pleasants, J.M, Oberhauser K. S. (2012) Milkweed loss in agricultural fields due to herbicide use: Effect on the Monarch Butterfly population. Insect Conservation and Diversity (March 12, doi: 10.1111/j.1752-4598.2012.00196x)

Oberhauser, K.S., Prysby, M.D., Mattila, H.R., Stanley-Horn, D.E., Sears, M.K., Dively, G., Olson, E., Pleasants, J.M., Lam, W.F. & Hellmich, R. (2001) Temporal and spatial overlap between monarch larvae and corn pollen. Proceedings of the National Academy of Sciences USA, 98, 11913– 11918.

Taylor O R, Shields J. The Summer Breeding Habitat of Monarch Butterflies in Eastern North America. (2000) Washington, DC: Environ. Protection Agency.

Notes: The figure (24 million acres) for the conversion of grassland, rangeland, wetlands and former CRP lands to cropland was obtained from two sources: Faber, Rundquist and Male (2012) data obtained from a USDA website summarizing cropland conversion in 2012 (2013). The former showed that 23.6 million acres had been converted to cropland from 2008 through 2011 and the later indicated that 398,223 acres had been converted in 2012. No figures are yet available for these conversions in 2013.

Plowed Under: How Crop Subsidies Contribute to Massive Habitat Losses (2012)
Scott Faber, Soren Rundquist and Tim Male. Environmental Working Group http://static.ewg.org/pdf/plowed_under.pdf (accessed 28 January 2014).

CROPLAND CONVERSION http://www.fsa.usda.gov/FSA/webapp?area=newsroom&subject=landing&topic=foi-er-fri-dtc (accessed 28 January 2014).