By Andrew Berry
A window to the world of global insect declines: Moth biodiversity trends are complex and heterogeneous. 2021. David L. Wagner, Richard Fox, Danielle M. Salcido, Lee A. Dyer. Proceedings of the National Academy of Sciences Jan 2021, 118 (2) e2002549117; https://DOI:10.1073/pnas.2002549117
Moths are the most taxonomically and ecologically diverse insect taxon for which there exist considerable time-series abundance data. There is an alarming record of decreases in moth abundance and diversity from across Europe, with rates varying markedly among and within regions. Recent reports from Costa Rica reveal steep cross-lineage declines of caterpillars, while other sites (Ecuador and Arizona, reported here) show no or only modest long-term decreases over the past two decades. Rates of decline for dietary and ecological specialists are steeper than those for ecologically generalized taxa. Additional traits commonly associated with elevated risks include large wingspans, small geographic ranges, low dispersal ability, and univoltinism; taxa associated with grasslands, aridlands, and nutrient-poor habitats also appear to be at higher risk. In temperate areas, many moth taxa limited historically by abiotic factors are increasing in abundance and range. We regard the most important continental-scale stressors to include reductions in habitat quality and quantity resulting from land-use change and climate change and, to a lesser extent, atmospheric nitrification and introduced species. Site-specific stressors include pesticide use and light pollution. Our assessment of global macrolepidopteran population trends includes numerous cases of both region-wide and local losses and studies that report no declines. Spatial variation of reported losses suggests that multiple stressors are in play. With the exception of recent reports from Costa Rica, the most severe examples of moth declines are from Northern Hemisphere regions of high human-population density and intensive agriculture.
Agricultural intensification and climate change are rapidly decreasing insect biodiversity. 2021. Peter H. Raven, David L. Wagner. Proceedings of the National Academy of Sciences Jan 2021, 118 (2) e2002548117; https://DOI.org/10.1073/pnas.2002548117
Major declines in insect biomass and diversity, reviewed here, have become obvious and well documented since the end of World War II. Here, we conclude that the spread and intensification of agriculture during the past half century is directly related to these losses. In addition, many areas, including tropical mountains, are suffering serious losses because of climate change as well. Crops currently occupy about 11% of the world’s land surface, with active grazing taking place over an additional 30%. The industrialization of agriculture during the second half of the 20th century involved farming on greatly expanded scales, monoculturing, the application of increasing amounts of pesticides and fertilizers, and the elimination of interspersed hedgerows and other wildlife habitat fragments, all practices that are destructive to insect and other biodiversity in and near the fields. Some of the insects that we are destroying, including pollinators and predators of crop pests, are directly beneficial to the crops. In the tropics generally, natural vegetation is being destroyed rapidly and often replaced with export crops such as oil palm and soybeans. To mitigate the effects of the Sixth Mass Extinction event that we have caused and are experiencing now, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice that empowers the less wealthy people and nations of the world, where the vast majority of us live, will be necessary.
Butterfly abundance declines over 20 years of systematic monitoring in Ohio, USA. 2019. Wepprich T, Adrion JR, Ries L, Wiedmann J, Haddad NM. PLoS ONE 14(7): e0216270. https://doi.org/10.1371/journal.pone.0216270
Severe insect declines make headlines, but they are rarely based on systematic monitoring outside of Europe. We estimate the rate of change in total butterfly abundance and the population trends for 81 species using 21 years of systematic monitoring in Ohio, USA. Total abundance is declining at 2% per year, resulting in a cumulative 33% reduction in butterfly abundance. Three times as many species have negative population trends compared to positive trends. The rate of total decline and the proportion of species in decline mirror those documented in three comparable long-term European monitoring programs. Multiple environmental changes such as climate change, habitat degradation, and agricultural practices may contribute to these declines in Ohio and shift the makeup of the butterfly community by benefiting some species over others. Our analysis of life-history traits associated with population trends shows an impact of climate change, as species with northern distributions and fewer annual generations declined more rapidly. However, even common and invasive species associated with human-dominated landscapes are declining, suggesting widespread environmental causes for these trends. Declines in common species, although they may not be close to extinction, will have an outsized impact on the ecosystem services provided by insects. These results from the most extensive, systematic insect monitoring program in North America demonstrate an ongoing defaunation in butterflies that on an annual scale might be imperceptible, but cumulatively has reduced butterfly numbers by a third over 20 years.
Declines in insect abundance and diversity: We know enough to act now. 2019. Forister, Matthew & Pelton, Emma & Hoffman Black, Scott. Conservation Science and Practice. 1. 10.1111/csp2.80. https://www.researchgate.net/publication/335554972_Declines_in_insect_abundance_and_diversity_We_know_enough_to_act_now
Recent regional reports and trends in biomonitoring suggest that insects are experiencing a multicontinental crisis that is apparent as reductions in abundance, diversity, and biomass. Given the centrality of insects to terrestrial ecosystems and the food chain that supports humans, the importance of addressing these declines cannot be overstated. The scientific community has understandably been focused on establishing the breadth and depth of the phenomenon and on documenting factors causing insect declines. In parallel with ongoing research, it is now time for the development of a policy consensus that will allow for a swift societal response. We point out that this response need not wait for full resolution of the many physiological, behavioral, and demographic aspects of declining insect populations. To these ends, we suggest primary policy goals summarized at scales from nations to farms to homes.
Ecological intensification to mitigate impacts of conventional intensive land use on pollinators and pollination. 2017. Kovács-Hostyánszki A, Espíndola A, Vanbergen AJ, Settele J, Kremen C, Dicks LV. Ecological Letters. 2017 May;20(5):673-689. doi: 10.1111/ele.12762. Epub 2017 Mar 27. PMID: 28346980; PMCID: PMC6849539. https://onlinelibrary.wiley.com/doi/full/10.1111/ele.12762
Worldwide, human appropriation of ecosystems is disrupting plant–pollinator communities and pollination function through habitat conversion and landscape homogenisation. Conversion to agriculture is destroying and degrading semi‐natural ecosystems while conventional land‐use intensification (e.g. industrial management of large‐scale monocultures with high chemical inputs) homogenises landscape structure and quality. Together, these anthropogenic processes reduce the connectivity of populations and erode floral and nesting resources to undermine pollinator abundance and diversity, and ultimately pollination services. Ecological intensification of agriculture represents a strategic alternative to ameliorate these drivers of pollinator decline while supporting sustainable food production, by promoting biodiversity beneficial to agricultural production through management practices such as intercropping, crop rotations, farm‐level diversification and reduced agrochemical use. We critically evaluate its potential to address and reverse the land use and management trends currently degrading pollinator communities and potentially causing widespread pollination deficits. We find that many of the practices that constitute ecological intensification can contribute to mitigating the drivers of pollinator decline. Our findings support ecological intensification as a solution to pollinator declines, and we discuss ways to promote it in agricultural policy and practice.
Few keystone plant genera support the majority of Lepidoptera species. 2020. Narango, D.L., Tallamy, D.W. & Shropshire, K.J. Nature Communications. 11, 5751. https://doi.org/10.1038/s41467-020-19565-4
Functional food webs are essential for the successful conservation of ecological communities, and in terrestrial systems, food webs are built on a foundation of coevolved interactions between plants and their consumers. Here, we collate published data on host plant ranges and associated host plant-Lepidoptera interactions from across the contiguous United States and demonstrate that among ecosystems, distributions of plant-herbivore interactions are consistently skewed, with a small percentage of plant genera supporting the majority of Lepidoptera. Plant identities critical for retaining interaction diversity are similar and independent of geography. Given the importance of Lepidoptera to food webs and ecosystem function, efficient and effective restoration of degraded landscapes depends on the inclusion of such ‘keystone’ plants.
Green Plants in the Red: A Baseline Global Assessment for the IUCN Sampled Red List Index for Plants. 2015. Brummitt, Neil & Bachman, Steven & Griffiths-Lee, Janine & Lutz, Maiko & Moat, Justin & Farjon, Aljos & Donaldson, John & Hilton-Taylor, Craig & Meagher, Thomas & Albuquerque, Sara & Aletrari, Elina & Andrews, A & Atchison, Guy & Baloch, Elisabeth & Barlozzini, Barbara & Brunazzi, Alice & Carretero, Julia & Celesti, Marco & Chadburn, Helen & Nic Lughadha, Eimear. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135152
Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question ‘How threatened are plants?’ is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the world’s plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed.
How many plant species are there, where are they, and at what rate are they going extinct? 2015. Pimm, Stuart L., and Lucas N. Joppa. Annals of the Missouri Botanical Garden 100.3 (2015): 170-176.
How many flowering plant species are there? Where are they? How many are going extinct, and how fast are they doing so? Interesting in themselves, these are questions at the heart of modern conservation biology. Determining the answers will dictate where and how successfully conservation efforts will be allocated. Plants form a large taxonomic sample of biodiversity. They are important in themselves and directly determine the diversity of many other taxonomic groups. Inspired by conversations with Peter Raven, we set out to provide quantitative answers to these questions. We argue that there are 450,000 species, two thirds of which live in the tropics, a third of all species are at risk of extinction, and they are going extinct 1000 to 10,000 times the background rate. In obtaining these results, we point to the critical role of dedicated taxonomic effort and biodiversity monitoring. We will only get a good answer to the age-old question of “how many species are there?” when we understand the population biology and social behavior of taxonomists. That most missing species will be found in biodiversity hotspots reaffirms their place as the foci of extinction for decades to come. Important, but not yet addressed, are future studies of how long plant species take to become extinct in habitat fragments. These will deliver not only better estimates of extinction rates, but also the critical timeframe of how quickly one needs to act to prevent extinctions.
How urbanization is driving pollinator diversity and pollination – A systematic review. 2020. Arne Wenzel, Ingo Grass, Vasuki V. Belavadi, Teja Tscharntke. Biological Conservation. Volume 241. https://doi.org/10.1016/j.biocon.2019.108321
Urban areas are growing worldwide and alter landscapes in a persistent fashion, thereby affecting biodiversity and ecosystem services such as pollination in a little understood way. Here we present a systematic review of the peer-reviewed literature to identify the drivers of urban pollinator populations and pollination. A total of 141 studies were reviewed and qualitatively analyzed. Pollinator responses to urbanization were contrasting. We contend that positive responses were often associated with urban sprawl, i.e. moderate levels of urbanization of rural, mostly agricultural land below 50% impervious surface, whereas high levels of densification with high percentages of sealed and built-up area (above 50%), largely led to pollinator declines and loss of pollination services. Further, urbanization generally reduced pollinator diversity when compared to natural or semi-natural areas, but enhanced it when compared to intensified agricultural landscapes. In addition, pollinator responses were commonly highly trait- and scale-specific. Cavity nesters and generalist species usually profited more from urbanization than ground nesters and specialists. Overall, urban pollinator communities still seem to provide sufficient pollination services to wild vegetation and crops. Pollinator diversity generally increased with the amount of urban green spaces at the landscape scale, and locally with availability of nesting resources and flowering plants. Positive effects of floral additions were largely independent of the plant’s origin, whether native or non-native. Only a few studies included landscape configuration. Likewise, abiotic urban drivers, e.g. heat island effects and air and light pollution, remain little studied. Tropical and developing regions, most heavily impacted by current and future urbanization, are strongly underrepresented. We conclude that biodiversity-friendly urbanization can make a valuable contribution to pollinator conservation, in particular in face of the continued intensification of rural agriculture.
Insect decline in the Anthropocene: Death by a thousand cuts. 2021. Wagner et al, Jan 2021. PNAS January 12, 2021 118 (2) e2023989118; https://doi.org/10.1073/pnas.2023989118
Nature is under siege. In the last 10,000 y the human population has grown from 1 million to 7.8 billion. Much of Earth’s arable lands are already in agriculture, millions of acres of tropical forest are cleared each year, atmospheric CO2 levels are at their highest concentrations in more than 3 million y, and climates are erratically and steadily changing from pole to pole, triggering unprecedented droughts, fires, and floods across continents. Indeed, most biologists agree that the world has entered its sixth mass extinction event, the first since the end of the Cretaceous Period 66 million y ago, when more than 80% of all species, including the nonavian dinosaurs, perished.
Ongoing losses have been clearly demonstrated for better-studied groups of organisms. Terrestrial vertebrate population sizes and ranges have contracted by one-third, and many mammals have experienced range declines of at least 80% over the last century. A 2019 assessment suggests that half of all amphibians are imperiled (2.5% of which have recently gone extinct. Bird numbers across North America have fallen by 2.9 billion since 1970. Prospects for the world’s coral reefs, beyond the middle of this century, could scarcely be more dire. A 2020 United Nations report estimated that more than a million species are in danger of extinction over the next few decades, but also see the more bridled assessments in refs. 10 and 11.
Although a flurry of reports has drawn attention to declines in insect abundance, biomass, species richness, and range sizes whether the rates of declines for insects are on par with or exceed those for other groups remains unknown. There are still too little data to know how the steep insect declines reported for western Europe and California’s Central Valley—areas of high human density and activity—compare to population trends in sparsely populated regions and wildlands. Long-term species-level demographic data are meager from the tropics, where considerably more than half of the world’s insect species occur. To consider the state of knowledge about the global status of insects, the Entomological Society of America hosted a symposium at their Annual Meeting in St. Louis, Missouri, in November 2019. The Society was motivated to do so by the many inquiries about the validity of claims of rapid insect decline that had been received in the months preceding the annual meeting and by the many discussions taking place among members. The entomological community was in need of a thorough review and the annual meeting provided a timely opportunity for sharing information.
The goal of the symposium was to assemble world experts on insect biodiversity and conservation and ask them to report on the state of knowledge of insect population trends. Speakers were asked to identify major data gaps, call attention to limitations of existing data, and evaluate principal stressors underlying declines, with one goal being to catalyze activities aimed at mitigating well-substantiated declines. All 11 talks were recorded and are available on the Entomological Society of America’s website, https://www.entsoc.org/insect-decline-anthropocene. Although this special PNAS volume is anchored to the St. Louis presentations, that effort is extended here to include new data, ideas, expanded literature reviews, and many additional coauthors.
Insect pollinators collect pollen from wind‐pollinated plants: implications for pollination ecology and sustainable agriculture. 2018. Saunders, M.E. Insect Conserv Divers, 11: 13-31. https://doi.org/10.1111/icad.12243
Current research, management and outreach programs relevant to insect pollinator conservation are strongly focused on relationships between pollinators and insect-pollinated crops and wild plants. Pollinators also visit wind-pollinated plants to collect pollen, or for nest sites and materials, but these interactions are largely overlooked. I review documented records of bee and syrphid fly species collecting pollen from wind-pollinated plant taxa, including economically important crops, and provide the most comprehensive collation of peer-reviewed records of pollinators visiting wind-pollinated plants to date. I argue for more basic research into functional relationships between insect pollinators and wind-pollinated plants. I found over 200 visitation records for 101 wind-pollinated plant genera in 25 families, including 4 of the 12 gymnosperm families. Almost half the records (49%) were for grasses and sedges (Poales). I also identified records of bees and/or syrphid flies visiting 10 economically important wind-pollinated crop plant species, including three major grain crops (rice, corn, and sorghum). Most records (70%) were from indirect pollen analysis from hives, nest cells or insect bodies, highlighting the need for more direct observational studies of plant-pollinator interactions. Insect pollinator communities require resource diversity to persist in a landscape. Hence, researchers and land managers aiming to identify links between pollinators and ecosystem function should also consider broader interactions beyond the standard traits of the entomophily syndrome.
Kentucky Monarch Conservation Plan. Kentucky Fish and Wildlife Resources, et al. 2018. Rogers, Michaela, et al. https://fw.ky.gov/Wildlife/Documents/ky_monarch_plan.pdf
The iconic monarch butterfly, well known for its striking orange-enveloped wings contrasted by black venation, has become an insect of high intrigue across North America. The marathon-length migration the butterfly makes to Mexico to overwinter in the alpine oyamel fir forests inspires wonder and fascination. The biological mechanisms and evolutionary relevance of this journey have become the subject of scientific research, while first sighting of the adults, eggs and caterpillars each year draws excitement from community scientists who participate in observation recording.
Recently, the monarch butterfly has garnered even greater attention. News broke on December 15, 2020 that the United States Fish and Wildlife Service (USFWS) had come to a decision on the federal listing status of the monarch butterfly. The Service had been petitioned in 2014 to list the monarch as a threatened species under the Endangered Species Act. Following comprehensive review of the current and future population status of the monarch butterfly, USFWS announced that listing the monarch as threatened or endangered is warranted, but precluded while higher priority listing actions are addressed.
This action results in the monarch becoming a candidate species under the Endangered Species Act. As a candidate species, the status of the monarch butterfly will now be reviewed yearly by USFWS scientists until a listing decision can be made. The monarch will likely stay in the national spotlight for years to come, during which time data collection will continue to assess the population and habitat created or improved for the butterfly.
The Kentucky Department of Fish and Wildlife Resources views the U.S. Fish and Wildlife Service’s decision as an indication of the vulnerable status of the species and as affirmation in the need for continued conservation work for the monarch. Conservation of the species will require efforts throughout the monarch’s range. Here in the state, we are moving forward with work on monarch preservation. Kentucky not only supports the iconic migration of the monarch, but serves as breeding habitat within the butterfly’s range.
Kentucky embarked on creation of the Kentucky Monarch Conservation Plan in 2016 following a targeted national effort surrounding concerns of population-level decline. During this time, garden clubs, native plant groups, and other organizations were already making headway for monarchs in the state. Published in 2018, this plan guides current priorities for monarch conservation, and will continue to do so through potential future changes in the listing status of the butterfly. Kentucky is also a member state in the Mid-America Monarch Conservation Plan, allowing for collaboration with other states across the monarch’s midwestern range to increase habitat. Of primary concern is increasing the number of milkweed stems in the region, which provide the sole food source of monarch caterpillars.
Currently, stakeholders of the Monarch Plan are working to increase habitat, which includes both milkweed and native flowering plants (a source of nectar resources for adult butterflies) on the landscape. There are now 827 Monarch Waystations officially registered in Kentucky, and thousands of acres of habitat have been improved or added for the benefit of monarchs and other pollinators through the enhancement of private, public, and right-of-way land. A variety of educational events and outreach initiatives have been aimed at raising awareness for the monarch in the state, with several hundred monarchs tagged over the course of fall tagging events, over a thousand seed packets distributed, and presentations given in classrooms, during workshops, at club and professional meetings, and most recently, in virtual settings.
Conserving the monarch butterfly has been called an “all hands on deck” approach, with participation from the transportation and agricultural sectors, public agencies, non-government organizations, private businesses, and urban, suburban and rural environments all being important in support of such a widespread species.
Planting milkweed is one of the most important things you can do to help the monarch. If you don’t have a garden, you can aid instead by participating in community science initiatives that track monarchs along their migration route (visit monarchjointventure.org and journeynorth.org to learn about opportunities). Follow us on Facebook at “Kentucky Monarchs” as we share information and links related to monarch butterflies in Kentucky, and remember that no effort is too small to help conserve monarchs!
Kentucky Pollinator Handbook. 2016. USDA-NRCS. https://efotg.sc.egov.usda.gov/references/public/KY/KPH5a.pdf
Kentucky Pollinator Protection Plan. 2019. Kentucky Farm Bureau. https://www.kyagr.com/statevet/documents/OSV_Bee_KY-Pollinator-Pro-Plan.pdf
Since 2015, stakeholders have met in an effort to enhance pollinator health in the Commonwealth by making available best management plans to beekeepers, chemical applicators, and landowners; increasing pollinator habitat; supporting education, extension and outreach; and facilitating communication among all entities that impact pollinators. These goals are intended to be inclusive of all pollinators.
Landscape impacts on pollinator communities in temperate systems: evidence and knowledge gaps. 2017. Senapathi, D., Goddard, M.A., Kunin, W.E. and Baldock, K.C.R. Functional Ecology. 31: 26-37. https://doi.org/10.1111/1365-2435.12809
- This review assesses current knowledge about the interplay between landscape and pollinator communities. Our primary aim is to provide an evidence base, identify key gaps in knowledge and highlight initiatives that will help develop and improve strategies for pollinator conservation.
- Human‐dominated landscapes (such as arable land and urban environments) can have detrimental impacts on pollinator communities but these negative effects can be ameliorated by proximity to semi‐natural habitat and habitat corridors. There is also evidence to suggest that increased landscape heterogeneity and landscape configuration can play an important role in the maintenance of diverse pollinator communities.
- Landscape characteristics have direct impacts on pollinator communities, but can also influence abundance and richness through interaction with other drivers such as changing climate or increased chemical inputs in land management.
- The majority of existing literature focuses on specific hymenopteran groups, but there is a lack of information on the impact of landscape changes on non‐bee taxa. Research is also needed on the effectiveness of management interventions for pollinators and multiple year observations are required for both urban and rural initiatives.
- Current policies and monitoring schemes could contribute data that will plug gaps in knowledge, thus enabling greater understanding of relationships between landscapes and pollinator populations. This would in turn help design mitigation and adaptation strategies for pollinator conservation.
Petition to protect the monarch butterfly (Danaus plexippus plexippus) under the endangered species act. 2014. https://ecos.fws.gov/docs/petitions/92210//730.pdf
The monarch is an iconic large orange and black butterfly that is one of the most familiar butterflies in North America. During summer monarchs can be found throughout the United States and southern Canada in most places where milkweeds (Asclepias spp.), their host plants, are available. Each year monarchs undertake a spectacular multi-generational migration of thousands of miles to and from overwintering and breeding areas. Most monarchs east of the Rocky Mountains migrate from southern Canada and the northern United States to the mountains of interior Mexico to overwinter. Most monarchs west of the Continental Divide migrate to coastal California.
Monarchs east and west of the Rocky Mountains now face significant threats to their survival in both their summer and winter ranges, and their numbers have declined precipitously in recent years. Overall the North American monarch population has declined by more than 90 percent in the past two decades based on comparisons of the most recent population size estimates to the 20-year average. Numbers of monarchs east of the Rockies have declined by more than 90 percent since 1995; at most recent count, in winter 2013-2014, monarchs east of the Rockies dropped to the lowest number yet recorded, continuing the progression toward declining numbers seen over the last decade. Similarly, numbers of monarchs west of the Rockies have declined by more than 50 percent since 1997. The significant threats facing the monarch are high in magnitude and ongoing.
In recognition of the dire status of this symbolic animal, in June 2014 the White House issued a Presidential Memorandum creating a federal strategy to promote the health of honey bees and other pollinators including the monarch. Although this is an important acknowledgement of the large-scale issues that are threatening the monarch, much more tangible action is needed to protect the butterfly and its habitat. Specifically, protecting this iconic species under the Endangered Species Act is a step that should be immediately taken to safeguard and recover the monarch.
The Endangered Species Act (ESA) allows species to be listed as “threatened” when they are at risk of becoming endangered in a significant portion of their range. The ESA defines an endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range” and a threatened species as “any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.” As applied here, the language of the statute, its legislative history and congressional intent, and the relevant judicial precedent interpreting and applying the statute all make clear that a species need not be at risk of worldwide extinction to qualify for ESA protection. Rather, in enacting the “significant portion of range” provision, Congress intended to provide a means to protect species before they are on the brink of extinction, which is of paramount importance to species conservation.
The best available scientific information indicates that the monarch butterfly is threatened in a significant portion of its range. The North American monarch population is significant because without it, the redundancy, resiliency, and representation of the species would be so impaired that the monarch would have an increased vulnerability to extinction. The migratory butterflies in eastern and western North America represent the vast majority of all monarchs in the world.
Though monarchs are found in relatively small, peripheral, and introduced populations in tropical and subtropical locations outside of North America (see Appendix A), these non- migrating populations cannot conserve the genetic diversity and spatial distribution of the species, are limited in population growth potential such that they cannot substitute for the abundance of the continental North American population, and are themselves vulnerable to extirpation.
Numerous species have been protected under the ESA that have large ranges and relatively abundant population sizes but that have experienced population decline and that face significant threats to their continued existence. A few examples of such species include the gray bat (Myotis grisescens), Indiana bat (Myotis sodalis), fat pocketbook mussel (Potamilus capax), piping plover (Charadrius melodus), Chinook salmon (Oncorhynchus (=Salmo) tshawytscha), and small whorled pogonia flower (Isotria medeoloides). A species is not required to have declined to the level of range-wide endangerment in order to qualify for protection under the ESA.
The ESA states that a species shall be determined to be endangered or threatened based on any one of five factors (16 U.S.C. § 1533 (a)(1)): 1) the present or threatened destruction, modification, or curtailment of its habitat or range; 2) overutilization for commercial, recreational, scientific, or educational purposes; 3) disease or predation; 4) the inadequacy of exisiting regulatory mechanisms; and 5) other natural or manmade factors affecting its contined existence. The monarch is threatened by all five of these factors and thus warrants protection
under the Act:
Pollinator Diversity: Distribution, Ecological Function, and Conservation. Ollerton, Jeff. (2017). Annual Review of Ecology, Evolution, and Systematics. 48. 10.1146/annurev-ecolsys-110316-022919.
By facilitating plant reproduction, pollinators perform a crucial ecological function that supports the majority of the world’s plant diversity, and associated organisms, and a significant fraction of global agriculture. Thus, pollinators are simultaneously vital to supporting both natural ecosystems and human food security, which is a unique position for such a diverse group of organisms. The past two decades have seen unprecedented interest in pollinators and pollination ecology, stimulated in part by concerns about the decline of pollinator abundance and diversity in some parts of the world. This review synthesizes what is currently understood about the taxonomic diversity of organisms that are known to act as pollinators; their distribution in both deep time and present space; the importance of their diversity for ecological function (including agro-ecology); changes to diversity and abundance over more recent timescales, including introduction of non-native species; and a discussion of arguments for conserving their diversity.
The decline of butterflies in Europe: Problems, significance, and possible solutions. 2021. Martin S. Warren, Dirk Maes, Chris A. M. van Swaay, Philippe Goffart, Hans Van Dyck, Nigel A. D. Bourn, Irma Wynhoff, Dan Hoare, and Sam Ellis. PNAS January 12, 2021 118 (2) e2002551117; https://doi.org/10.1073/pnas.2002551117
We review changes in the status of butterflies in Europe, focusing on long-running population data available for the United Kingdom, the Netherlands, and Belgium, based on standardized monitoring transects. In the United Kingdom, 8% of resident species have become extinct, and since 1976 overall numbers declined by around 50%. In the Netherlands, 20% of species have become extinct, and since 1990 overall numbers in the country declined by 50%. Distribution trends showed that butterfly distributions began decreasing long ago, and between 1890 and 1940, distributions declined by 80%. In Flanders (Belgium), 20 butterflies have become extinct (29%), and between 1992 and 2007 overall numbers declined by around 30%. A European Grassland Butterfly Indicator from 16 European countries shows there has been a 39% decline of grassland butterflies since 1990. The 2010 Red List of European butterflies listed 38 of the 482 European species (8%) as threatened and 44 species (10%) as near threatened (note that 47 species were not assessed). A country level analysis indicates that the average Red List rating is highest in central and mid-Western Europe and lowest in the far north of Europe and around the Mediterranean. The causes of the decline of butterflies are thought to be similar in most countries, mainly habitat loss and degradation and chemical pollution. Climate change is allowing many species to spread northward while bringing new threats to susceptible species. We describe examples of possible conservation solutions and a summary of policy changes needed to conserve butterflies and other insects.
The Little Things That Run the World. 1987. Wilson, E.O. (The Importance and Conservation of Invertebrates). Conservation Biology, 1: 344-346. https://doi.org/10.1111/j.1523-1739.1987.tb00055.x
It needs to be repeatedly stressed that invertebrates as a whole are even more important in the maintenance of ecosystems than are vertebrates.
Reserves for invertebrate conservation are practicable and relatively inexpensive. Many species can be maintained in large, breeding populations in areas too small to sustain viable populations of vertebrates. A 10-ha plot is likely to be enough to sustain a butterfly or crustacean species indefinitely. The same is true for at least some plant species. Consequently, even if just a tiny remnant of natural habitat exists, and its native vertebrates have vanished, it is still worth setting aside for the plants and invertebrates it will save.
The ex-situ preservation of invertebrate species is also very cost-effective. A single pair of rare mammals typically costs hundreds or thousands of dollars yearly to maintain in a zoo (and worth every penny!). At the same time, large numbers of beautiful tree snails, butterflies, and other endangered in vertebrates can be cultured in the laboratory, often in conjunction with public exhibits and educational programs, for the same price.
It will be useful to concentrate biological research and public education on star species when these are available in threatened habitats, in the manner that has proved so successful in vertebrate conservation.
Trees for bees. Donkersley, Philip. Agriculture, Ecosystems & Environment. Volume 270–271. 2019. Pages 79-83. https://doi.org/10.1016/j.agee.2018.10.024
Limited resources and land-use pressures require more efficient conservation strategies, from increasingly limited input. Pollinator declines are threatening food security and natural capital. I present a novel perspective on landscape level pollinator conservation from across multiple scientific fields. I examine the value of landscape structure provided by trees and hedgerows compared with floral strips, and discuss use of computer simulation technologies for understanding how spatial structure impacts pollinators’ ability to forage.
All bees forage on a mixture of both flowering plants and tree species. Honeybees have a detectable preference for foraging on trees, even when sparse. The spatial information provided by trees and hedgerows positively impacts formation of the “cognitive map”, making pollination and foraging more efficient. Woody habitat features like trees and hedgerows provide more efficient resources for pollinators in a number of ways. They are more efficient forage targets due to absolute resource density; tree and hedgerow planting could provide more optimised foraging landscapes for pollinators. Using computer simulation may enable us to study pollinator responses to landscape development at this scale. Woodland development results in non-pollinator ecosystem services, representing a more cost-effective conservation strategy. Moving forward we need to identify the key impediments to its successful implementation.
By facilitating plant reproduction, pollinators perform a crucial ecological function that supports the majority of the world’s plant diversity, and associated organisms, and a significant fraction of global agriculture. Thus, pollinators are simultaneously vital to supporting both natural ecosystems and human food security, which is a unique position for such a diverse group of organisms. The past two decades have seen unprecedented interest in pollinators and pollination ecology, stimulated in part by concerns about the decline of pollinator abundance and diversity in some parts of the world. This review synthesizes what is currently understood about the taxonomic diversity of organisms that are known to act as pollinators; their distribution in both deep time and present space; the importance of their diversity for ecological function (including agro-ecology); changes to diversity and abundance over more recent timescales, including introduction of non-native species; and a discussion of arguments for conserving their diversity.
To mow or to mow less: Lawn mowing frequency affects bee abundance and diversity in suburban yards. 2018. Lerman, Susannah & Contosta, Alix & Milam, Joan & Bang, Christofer. Biological Conservation. 221. 10.1016/j.biocon.2018.01.025. https://www.fs.fed.us/nrs/pubs/jrnl/2018/nrs_2018_Lerman_001.pdf
Green spaces embedded within the urban matrix, particularly residential yards, could mitigate negative aspects of urban development and provide pollinator habitat. Lawns represent a dominant green space, and their management consists of frequent mowing to inhibit the growth of ostensibly “weedy” species (e.g., dandelions and clover). Since widespread population declines of bees and other pollinators from habitat loss are a growing concern, these spontaneous flowers could provide pollen and nectar sources throughout the growing season. We experimentally tested whether different lawn mowing frequencies (1, 2 or 3 weeks) influenced bee abundance and diversity in 16 suburban western Massachusetts yards by increasing lawn floral resources. Lawns mowed every three weeks had as much as 2.5 times more lawn flowers than the other frequencies. Interestingly, lawns mowed every two weeks supported the highest bee abundance yet the lowest bee richness and evenness. We suggest these patterns were driven by a combination of more abundant floral resources (compared with 1-week yards), easier access to lawn flowers due to shorter grass and a more drastic impact on grass biomass and floral resources (compared with 3-week yards), and the dominance of a few generalist bees overwhelming our samples, thus driving richness and evenness. Our results highlight a “lazy lawnmower” approach to providing bee habitat. Mowing less frequently is practical, economical, and a timesaving alternative to lawn replacement or even planting pollinator gardens. Given the pervasiveness of lawns coupled with habitat loss, our findings provide immediate solutions for individual households to contribute to urban conservation.
