“...It is not too late to make a difference, but only if we start now at every level from local to global… Through ‘transformative change’, nature can still be conserved…”
Sir Robert Watson, Chair of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), United Nations Sustainable Development Blog
Why We’re So Focused
On Wild/Native Gardens
It’s estimated that bird abundance in the U.S. has seen a 30% decline since 1970 (estimated 2.9 billion birds)1, and where we have data, it seems that insect abundance has declined by about 45% in the last 40 years (2). In Vermont, for example, a 2014 survey from the Vermont Center for Ecostudies found that half of Vermont’s 17 bumblebee species were declining or had disappeared from the state (5 species had disappeared)(3), and VCE’s recent wild bee survey concluded that 30% of Vermont wild bees are imperiled or critically imperiled(4).
One of the largest drivers of these declines is habitat loss and degradation. For both birds and pollinators, having enough habitat and food resources is directly connected to having enough native plants and flowers on the landscape. Interesting food web dynamics have been shown in recent years by Doug Tallamy’s entomology lab at University of Delaware, where they have been studying the connections between song birds, caterpillars, and native plants. Apparently, 96% of North American birds feed their nestlings primarily insects, and largely caterpillars (which are soft and full of protein), during the breeding season(5). However, about 90% of insect species are specialists, meaning most can only eat certain species of native plants(5).
This specialization is the evolutionary result of plants evolving defenses against being eaten, and insects evolving specialized adaptations to keep eating them, such as specialized mouthparts or specialized metabolism, in response to plants’ physical and chemical defenses. Monarch butterflies are a famous example of an insect overcoming a plant’s toxicity, but the story of specialization holds true throughout the world of herbivorous insects.
Native plants and the insects who eat them form the base of food webs and are fundamental to the function of an ecosystem. As native plants have been displaced through agricultural expansion, urban and suburban development, and increased levels of invasive species in natural areas, we are seeing this reduction in food resources ripple throughout higher order animals.
The need to restore habitat is being recognized in the realm of policy. In line with targets from the recent landmark UN Global biodiversity framework, the Biden administration signed an executive order in January of 2021, calling for conserving and restoring 30% of U.S. land and oceans by 2030 (6), a stepping stone to 50% of land conserved and restored by 2050. Through very well-established models, it is thought this level of habitat conservation is needed for 85% of species on earth to survive(7). As luck would have it, restoring and conserving land is also one of the best ways to reduce and sequester carbon dioxide emissions(8).
These sad trends in pollinator and bird populations can be reversed, but it will require a broad cultural shift, from maintaining exclusively human spaces, to creating places where both humans and the natural world can coexist. Tallamy’s lab has demonstrated that yards that participate in backyard habitat programs really do make a difference(9):
Native gardens support significantly more caterpillars (bird food), and caterpillar species;
Native gardens show significantly greater bird abundance, diversity, biomass, and breeding pairs of native bird species;
And importantly, bird species of regional conservation concern were 8 times more abundant and more diverse on properties with native landscaping.
Lucky for us, replacing areas of lawn with native gardens not only creates habitat for wildlife, but also creates a space that is more fun, more beautiful, and so much more engaging for people (all while reducing lawn mower emissions and sequestering carbon dioxide).
References
1 Rosenberg, Kenneth V., et al. "Decline of the North American avifauna." Science 366.6461 (2019): 120-124.
https://par.nsf.gov/servlets/purl/10133018
2 Wagner, David L., et al. "Insect decline in the Anthropocene: Death by a thousand cuts." Proceedings of the National Academy of Sciences 118.2 (2021). https://www.pnas.org/doi/10.1073/pnas.2023989118
3 McFarland, K.P., L. Richardson, and S. Zahendra. 2015. Vermont Bumble Bee Atlas. Vermont Center for Ecostudies – Vermont Atlas of Life.
http://val.vtecostudies.org. Retrieved 4/6/22.
4 Hardy, Spencer, Michael T. Hallworth, Mark Ferguson, Nathaniel Sharp, Jason Loomis, Emily Anderson, Kent McFarland. 2022. The State of Vermont’s Wild Bees 2022. https://stateofbees.vtatlasoflife.org/. Vermont Center for Ecostudies-Vermont Atlas of Life. Accessed: 3/4/2023
5 Tallamy, Doug. Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens. Timber Press Inc., 2007.
6 Conserving and Restoring America the Beautiful
7 Wilson, Edward O. Half-earth: Our Planet's Fight for Life., Liveright., 2016.
8 Dinerstein, Eric, et al. "A global deal for nature: guiding principles, milestones, and targets." Science advances 5.4 (2019): eaaw2869.
https://www.science.org/doi/full/10.1126/sciadv.aaw2869
9 Burghardt, Karin T., Douglas W. Tallamy, and W. Gregory Shriver. "Impact of native plants on bird and butterfly biodiversity in suburban landscapes." Conservation biology 23.1 (2009): 219-224.
https://conbio.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/j.1523-1739.2008.01076.x