Insect Decline-Evaluation of Potential Drivers of a Complex Phenomenon.

The decline of insects is a global concern, yet identifying the factors behind it remains challenging due to the complexity of potential drivers and underlying processes, and the lack of quantitative historical data on insect populations. This study assesses 92 potential drivers of insect decline in West Germany, where significant declines have been observed. Using data from federal statistical offices and market surveys, the study traces changes in landscape structure and agricultural practices over 33 years.

Connectivity increases trophic subsidies in fragmented landscapes.

Landscape corridors mitigate the negative effects of habitat fragmentation by increasing dispersal. Corridors also increase biodiversity in connected habitat fragments, suggestive of metacommunity dynamics. What is unknown in this case is the mechanisms through which metacommunity dynamics act.

Connectivity from a different perspective: comparing seed dispersal kernels in connected vs. unfragmented landscapes.

Habitat fragmentation can create significant impediments to dispersal. A technique to increase dispersal between otherwise isolated fragments is the use of corridors. Although previous studies have compared dispersal between connected fragments to dispersal between unconnected fragments, it remains unknown how dispersal between fragments connected by a corridor compares to dispersal in unfragmented landscapes.

Differential effects of habitat isolation and landscape composition on wasps, bees, and their enemies.

Habitat loss and fragmentation are major threats to biodiversity and ecosystem functioning. Effects of these usually intercorrelated processes on biodiversity have rarely been separated at a landscape scale. We studied the independent effects of amount of woody habitat in the landscape and three levels of isolation from the next woody habitat (patch isolation) on trap nesting bees, wasps, and their enemies at 30 farmland sites in the Swiss plateau.