No-bees’ land: habitat loss and fragmentation leave pollinators stranded

Pollinators depend on their natural surroundings for food and nesting sites. Most pollinators are insects (bees, flies, moths, butterflies, beetles), but select birds and mammals also provide essential pollination services. Each pollinator species has a unique life history and specific habitat needs. Unfortunately, human activities have reduced the quantity and quality of pollinator habitat worldwide. At the same time, global warming threatens the remaining habitat.

Habitat loss and fragmentation

Today, humans have altered more than half of the world's terrestrial land, with the majority of land conversion due to agricultural development.1 Human activities have fragmented the landscape into heavily developed tracts, wildlife preserves and everything in-between. Not surprisingly, habitat loss is strongly correlated with declines in biodiversity. The size and shape of the remaining habitat fragments, as well as how they connect to each other, affect how much wildlife they can support.2

Habitat fragment size varies widely, from inner city gardens to wildflower meadows. In general, smaller fragments offer fewer floral or nesting resources to pollinators when compared to larger fragments. The smaller pollinator populations that result are more susceptible to environmental stressors like drought or disease. These challenges can prevent some pollinator species from persisting on small fragments, especially on fragments that are poorly connected to larger habitat patches. Close or well-connected fragments create a habitat network, increasing the resources available to resident pollinators. Conversely, greater distances between fragments limits or prevents pollinators from accessing the resources in detached habitats. Species with strong flight capabilities pay an energetic toll to reach disjointed habitats. Meanwhile, weak fliers that are unable to reach distant fragments may face local extinction.

Fragment shape and neighboring land use also affect pollinator habitat quality. The unique environment present where two habitats meet can support a distinct biological community. Such “edge effects" can have positive or negative effects on pollinators. For example, the shaded edge of a field bordering a forest might promote the growth of diverse blooming plants, supporting the local pollinator community. However, the edge of a natural field bordering an agricultural plot could be contaminated by pesticides, posing exposure risks to pollinators. Edge effects can be magnified by a habitat fragment's shape. For example, long and narrow land parcels have a longer perimeter than do condensed, circular land parcels of the same area.

The negative effects of habitat loss and fragmentation are magnified by global warming. Changing weather patterns may degrade the quality of remaining habitat. Furthermore, as average temperatures rise, the habitable range for many species is predicted to shift. However, some species may have difficulty moving to new territory in a highly fragmented landscape.3

The challenges of habitat enhancement, restoration and conservation

Plant-57.jpgConservation resources are limited. Thus, the strategic identification of where, when and how to enhance, restore or conserve habitat is important. Both experiments and environmental monitoring aid conservation efforts. Some experiments can identify conservation practices that are likely to succeed in a relatively short period of time. Meanwhile, monitoring can determine where habitat exists and assess its quality. If habitat is enhanced or restored, long-term monitoring also provides information about the effectiveness of the conservation strategies used. Climate modeling can also help project where shifting environmental conditions are mostly likely to harm or support target species. Unfortunately, gathering enough information to identify
meaningful trends and effective management practices can be a lengthy process. Conservation biology, however, has a rich history of enlisting citizen scientists to collect data. Today, technology offers the public unprecedented opportunities to participate in large-scale monitoring projects to support conservation efforts.

Beyond monitoring, researchers are also grappling with the science of how to best enhance, restore and maintain the many, diverse pollinator habitats found worldwide. For example, native tallgrass prairie, once abundant through North America and home to over 300 species of flowering plants, now only covers 4% of its original 170-million acre range.4,5 Prairie restorations require seed supplies of native plants, which are not typically produced at commercial scales. Careful study of floriculture and seed propagation techniques, and concerted efforts to harvest and distribute seed from restoration efforts, are the rewards of decades of dedicated scientific research.6

How can you help reverse habitat loss and fragmentation?

  1. Plant pollinator habitat! Whether you are planting a pollinator garden in your yard or enrolling farmland in the NRCS Conservation Reserve Program, you can take action to support pollinators by creating habitat for them today! The Xerces Society for Invertebrate Conservation provides guidance for creating or enhancing pollinator habitat in natural lands; cities and towns; roadsides and other rights-of way; yards and gardens; and working lands. Information about regionally appropriate native plants is also available through the Xerces Pollinator Conservation Resource Center. The P4 Plan also offers guidance. If you're not sure how best to get involved, reach out to your local university's extension program for ideas and help.
  2. Participate in citizen science. Monitor pollinators and their habitat! The data you contribute will support research efforts to conserve pollinators and the resources they need. You can select a program that matches your interests and availability.
  3. Support conservation organizations that restore habitat using science-based recommendations and best management practices.
  4. Notify your representatives that pollinator habitat is important!

References

  1. Ellis, E. C., Klein Goldewijk, K., Siebert, S., Lightman, D. & Ramankutty, N. Anthropogenic transformation of the biomes, 1700 to 2000. Glob. Ecol. Biogeogr. 19, 589–606 (2010).

  2. Fahrig, L. Effects of habitat fragmentation on biodiversity. Annu. Rev. Ecol. Evol. Syst. 34, 487–515 (2003).

  3. Honnay, O. et al. Possible effects of habitat fragmentation and climate change on the range of forest plant species. Ecol. Lett. 5, 525–530 (2002).

  4. National Park Service. A complex prairie ecosystem. Tallgrass Prairie (2018).

  5. Service, N. P. Last stand of the Tallgrass Prairie. Tallgrass Prairie (2020).

  6. Tallgrass Prairie Center at the University of Northern Iowa. Research and restoration. Prairie restoration (2020).