Biodiversity in retreat
Numerous studies in recent years show: Biodiversity in meadows and pastures has declined sharply in recent decades. Measures to halt this loss have so far mostly focused on species that live above ground, such as birds and bees. But the soil of meadows and pastures is also teeming with life. These organisms are at least as diverse as the above-ground fauna and immensely important for soil fertility, carbon storage, and a host of other ecosystem services.
The study by researchers at the Senckenberg Biodiversity and Climate Research Center Frankfurt analyzed how species-rich 150 plots in meadows and pastures are, both above and below ground, and what role intensive land use plays in this. The study areas were located in the Schorfheide-Chorin, on the Swabian Alb and in the Hainich National Park. For the study, species diversity along the entire food chain was correlated and considered, and it was also investigated how intensively the plots were used for agriculture and what the landscape looked like within a two-kilometer radius of the plots.
The research led to new findings regarding how soil biodiversity is affected: for example, soil biodiversity in agricultural meadows and pastures is highest when they are surrounded by forest with old-growth trees. In contrast, the two main pillars of agrobiodiversity policies - extensive land use and a diverse environment - have little impact on the diversity of sub-irid organisms. Accordingly, current pratices of nature conservation in agricultural landscapes, such as a reduced use of fertilizers or the planting of flower strips, have a positive impact on above-ground species such as bees or birds, but are unlikely to benefit life in the soil. This is because below- and above-irid biodiversity are subject to different influences.
How intensively plots are fertilized, grazed, or mowed has little effect on the species richness in the soil of the plots. Surprisingly, some groups of soil animals, such as fungi and amoebae, even benefit from intensive land use. Thus, according to the study, the species diversity of soil organisms depends less on what happens on the plot itself, but rather on the nature of the wider environment: this is higher the more forest land there is within two kilometers and the longer this forest has existed. Thus, forests provide a stable habitat for soil organisms and a place of refuge. From there, animals and fungi can recolonize the soil of meadows and pastures after agricultural practices have been implemented.
The study shown once again highlights the immense importance of agroforestry systems. For example, the cultivation of tree rows on fields leads to multiple positive effects such as increased resilience to drought and heavy rainfall, the regeneration of degenerated soils and the build-up of humus, thus ensuring an increase in soil biodiversity. Soil improvement and biodiversity conservation in agriculture thus succeeds first and foremost with agroforestry systems.