<p class="first" id="d18732831e322">Recent reports of local extinctions of arthropod
species1, and of massive declines
in arthropod biomass2, point to land-use intensification as a major driver of decreasing
biodiversity. However, to our knowledge, there are no multisite time series of arthropod
occurrences across gradients of land-use intensity with which to confirm causal relationships.
Moreover, it remains unclear which land-use types and arthropod groups are affected,
and whether the observed declines in biomass and diversity are linked to one another.
Here we analyse data from more than 1 million individual arthropods (about 2,700 species),
from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest
sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased
over time, indicating loss of species across sites and regions. In annually sampled
grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%,
respectively. The decline was consistent across trophic levels and mainly affected
rare species; its magnitude was independent of local land-use intensity. However,
sites embedded in landscapes with a higher cover of agricultural land showed a stronger
temporal decline. In 30 forest sites with annual inventories, biomass and species
number-but not abundance-decreased by 41% and 36%, respectively. This was supported
by analyses of all forest sites sampled in three-year intervals. The decline affected
rare and abundant species, and trends differed across trophic levels. Our results
show that there are widespread declines in arthropod biomass, abundance and the number
of species across trophic levels. Arthropod declines in forests demonstrate that loss
is not restricted to open habitats. Our results suggest that major drivers of arthropod
decline act at larger spatial scales, and are (at least for grasslands) associated
with agriculture at the landscape level. This implies that policies need to address
the landscape scale to mitigate the negative effects of land-use practices.
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