Agriculture can lead to major disturbances to ecological systems, and the recovery of formally used agricultural land can often take a long period of time. However, according to a new study published in the Journal of Ecology, without any active restoration efforts, this recovery can take an exceedingly long time and will frequently be incomplete. These findings shed new light on the recovery process at different scales in former agricultural sites, and identify specific restoration interventions which could assist in the recovery of plant diversity.
The scientists measured the recovery of plant diversity and species composition at 17 temperate grasslands in Minnesota that were previously ploughed and used for agricultural practices. Some of these fields were abandoned between 1927 and 2015 so that natural succession and recovery of the vegetation followed. However, by comparing these abandoned places with sites that were never ploughed, the experts found that the former had significant difficulties in returning to their pre-agricultural state.
“What we wanted to know was how fast and how completely disturbed grasslands can regain their biodiversity if they are left to recover. Understanding that recovery process can give us insights into how we can assist and speed it up using restoration,” said study lead author Emma Ladouceur, an ecologist and conservation biologist at the German Center for Integrative Biodiversity Research (iDiv).
The analysis revealed that, even after 80 years, the abandoned fields had not managed to recover fully on their own, and although the types of plant species initially present at the sites recovered over time, this process remained incomplete. At the beginning of the recovery process, the fields were colonized by species unique to old sites (such as weeds and other disturbance-tolerant species), followed by many species characteristic of the never-disturbed sites. Yet, across the whole study, there were 63 native species that were unique to the never-ploughed sites, while the recovering old fields had a larger number of introduced grasses and weeds.
These findings suggest that active restoration efforts are needed to help these ecosystems better recover. “By looking closely at the recovery of species composition at different scales, we can get a better idea of what species could be targeted in restoration treatments, and how we could help these systems recover best,” explained study co-author Stan Harpole, an expert in Biodiversity at iDiv.
“Specific restoration measures could include the seeding or planting of species that we know are not part of the composition of recovering fields, combined with the management of exotic species to reduce competition with native species,” concluded Ladoucer.
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