It may seem obvious that agriculture can have a big impact on the landscape and the composition of animal communities that live there, but it turns out that not a lot of research has been done to determine the long-term effects of land use on these communities. Researchers at Stanford University sought fill in that gap by conducting an 18-year study in Costa Rica to discover how land use change, specifically conversion to agriculture, affects biodiversity long after the initial conversion of the land. Looking specifically at birds, the researchers wanted to know how diversified and intensive agriculture affected the long-term composition of bird communities, and also how climate change together with land use changes impacted these communities.
What they found was that how we farm matters. It might be easy to lump diversified and intensive agriculture together in the same category, but they are actually very different in the ways they approach growing food. Diversified agriculture operations generally grow many different types of crops together, include other types of vegetation and are generally in close proximity to natural habitat areas. Intensive agricultural operations grow large amounts of one or two crops with little to no variety in vegetation type. Using naturally forested habitats as a baseline, researchers found that bird communities in diversified agricultural areas had a comparable level of species richness, or number of different species, to the naturally forested areas. Bird communities in intensively managed agricultural areas, on the other hand, had a species richness level that was 52% lower than forested habitats. Diversified agricultural habitats not only hosted more bird species overall, but they also supported more at-risk species and more endemic species, which are species that are unique to that area of Costa Rica. Researchers found that of the endemic and IUCN red listed species found in forested areas, 59% of those were also found in diversified agricultural areas while only 39% were found on intensively farmed lands. In terms of climate change implications, bird communities in natural and diversified agricultural areas did not seem to change in response to temperatures and precipitation. On the other hand, bird community composition in intensively farmed areas saw major shifts in response to temperature and precipitation.
This study shows just how large of an impact agriculture has on biodiversity, and how much we can positively impact the resilience of our plant and animal communities if we switch to more diversified methods. Stepping away from monocropping and instead growing different types of crops together in closer proximity to natural vegetation can protect species unique to different regions, support at-risk species, and create animal communities that are more stable and resilient in the face of environmental stressors caused by climate change.
Hendershot, J.N., Smith, J.R., Anderson, C.B. et al. Intensive farming drives long-term shifts in avian community composition. Nature 579, 393–396 (2020). https://doi.org/10.1038/s41586-020-2090-6