In a groundbreaking study, Princeton-led researchers have found that cropland abandonment can benefit biodiversity, but frequent recultivation and ongoing habitat loss complicate conservation efforts.
A new study led by Princeton University adds depth to the ongoing discussion about cropland abandonment’s effects on biodiversity, suggesting that its conservation potential is significant but compromised by frequent land recultivation and continuing habitat loss.
For decades, the expansion of agricultural land has been one of the most pervasive threats to terrestrial biodiversity, leading to the degradation of ecosystems worldwide. Interestingly, recent trends show substantial areas of cropland being abandoned due to factors like rural outmigration, urbanization and geopolitical conflicts.
The recent study, published in the journal Nature Sustainability, employs high-resolution annual land-cover maps of 11 sites across four continents from 1987 to 2017. By combining these maps with habitat preferences and range maps for over 1,300 species of birds and mammals, the team assessed the biodiversity consequences of cropland abandonment.
“Without detailed abandonment maps for broad areas over long time periods, it has been really difficult to get a comprehensive picture of how abandonment was affecting biodiversity,” lead author Christopher Crawford, formerly a postdoctoral research associate at Princeton and now a AAAS Science & Technology Policy Fellow at the U.S. Department of Agriculture, said in a news release. “By leveraging our cutting-edge abandonment maps and looking at entire communities of mammals and birds, with all of their unique preferences, we’ve been able to understand abandonment’s impacts on biodiversity in a more nuanced and detailed way than ever before.”
The findings reveal that a majority of bird (62.7%) and mammal species (77.7%) gained habitat due to cropland abandonment. However, even more species — 74.2% of birds and 86.3% of mammals — would have benefited if the lands had not been recultivated. Furthermore, recultivation alongside the creation of new cropland led to a net habitat loss for 32.3% of birds and 27.8% of mammals.
“In our previous research, we noted that abandoned fields were frequently recultivated,” co-author He Yin, an assistant professor of geography at Kent State University, said in the news release. “This study helps us understand the extent to which recultivation may impact conservation efforts when abandonment is used as a strategy.”
The research underscores the pivotal role that a species’ habitat preference plays in determining the outcome of cropland abandonment. Species that can thrive in a range of habitats, such as forests, grasslands or savannas, are more likely to benefit, whereas those dependent on cultivated land face habitat loss.
“Ultimately, the answer to the question if abandoned fields benefit biodiversity conservation depends on the population trends of all the species in a given area, and how much habitat is available to them elsewhere,” added co-author Volker Radeloff, a professor in the SILVIS lab at the University of Wisconsin-Madison. “Broad-brush statements about the conservation value of abandoned fields are bound to be wrong. What is required are species-specific analyses, like the ones we conducted.”
Although the study found generally positive outcomes from cropland abandonment for biodiversity, these benefits are often mitigated by frequent recultivation and ongoing agricultural expansion.
David Wilcove, a professor at Princeton’s School of Public and International Affairs and the Department of Ecology and Evolutionary Biology, highlighted the role of policymakers in maximizing the conservation potential of abandoned croplands.
“With millions of people around the world leaving rural areas to move to cities, we might expect the resulting land abandonment to provide great opportunities to restore ecosystems and biodiversity,” he said. “It can, but the benefits to nature won’t be realized if the abandoned cropland is recultivated. An important challenge for policymakers is to provide the right financial or social incentives so that abandoned, marginal croplands can regrow into natural ecosystems. At the same time, policymakers must ensure that the lands that stay in crop production produce enough food to feed a growing population.”
This study offers a compelling, data-driven perspective on the multifaceted impacts of cropland abandonment, advocating for nuanced, species-specific conservation strategies.