COS 10-1 - Rural land abandonment is too ephemeral to provide major benefits for biodiversity and climate, despite substantial potential to create habitat and store carbon.

Background/Question/Methods

Although agricultural expansion and deforestation continues to be a dominant, and concerning, land use trend in many regions, tens of millions of hectares of cropland have also been abandoned globally since 1950 due to shifting demographics, sociopolitical upheaval, environmental changes, and globalization. This abandonment has been seen as a vast source of land that could be used for carbon sequestration and habitat restoration without imposing significant opportunity costs. However, these environmental benefits depend on the longevity of abandonment, which is poorly known. Moreover, benefits to biodiversity also depend on the distribution of species and their habitats. As such, the extent to which abandonment presents an opportunity or a threat to biodiversity remains an unsettled debate. Here, we track abandonment and recultivation at eleven sites across four continents using high-resolution annual land cover maps for 1987 through 2017. These sites, each covering between 1.58-5.64 million hectares, represent areas with recent documented abandonment, spanning a range of biomes. To assess the environmental implications of abandonment, we combine these maps with (i) spatially-explicit estimates of potential carbon accumulation in forest biomass and soil organic carbon, and (ii) species range maps to estimate changes in area of habitat for 2023 bird and mammal species.

Results/Conclusions

We find the majority of bird (64.33%) and mammal (81.53%) species experience statistically significant gains in area of habitat as a direct result of cropland abandonment. However, we find that abandonment is almost always fleeting, lasting on average only 14.22 years (SD = 1.44). By modeling the recultivation (or “decay”) of abandonment as a function of the time since abandonment, we project that >50% of abandoned croplands at most sites will be recultivated within 30 years, limiting their ability to accumulate substantial amounts of carbon and biodiversity. Recultivation observed during our time series resulted in 13-55% less area and 23-52% less carbon sequestered in abandoned croplands by 2017 than would have been possible without recultivation. Similarly, a greater share of birds (74.85%) and mammals (89.16%) would have seen significant gains in habitat without recultivation. More concerningly, however, habitat gains from abandonment do not compensate for habitat loss that took place prior to abandonment or throughout each site; when considering these changes, the majority of species show negative trends in habitat. Despite substantial potential, unless policymakers take steps to reduce habitat loss and recultivation, abandonment will remain a missed opportunity to reduce biodiversity loss and climate change.