Insects are vital for the functioning of ecosystems, but they are also facing a global decline due to various factors such as habitat loss, pollution, biological invasions, and climate change.
However, a new study published in Nature reveals that weather conditions and their fluctuations over time can also have a significant impact on insect biomass and diversity.
The researchers used sample-specific information on weather conditions during sampling and weather anomalies during the insect lifecycle to explain the variation in temporal decline in insect biomass, including an observed increase in biomass in recent years.
The results showed that insects react sensitively when temperature and precipitation deviate from the long-term average. In an unusually dry and warm winter, their survival probabilities are reduced; in a wet and cold spring, hatching success is impaired.
A cool, wet summer hampers bumblebees and other flying insects to reproduce and forage. If several such weather anomalies occur in combination and over several years, this can lead to a decline in insect biomass on a large scale and in the long term.
The researchers found that weather variables alone could explain the variation in insect biomass over time, without considering other factors such as land use or habitat quality.
This suggests that weather conditions and their changes due to climate change are important drivers of global insect decline.
Weather affects insect diversity differently across regions
The study also compared the effects of weather on insect diversity across different regions in Germany, using data collected from flying insects with 20 malaise traps across a landscape mosaic consisting of organic and conventional farmland, as well as agricultural land that has been recently converted from conventional to organic farming.
The researchers analyzed operational taxonomic units (OTUs) and barcode index numbers (BINs) via metabarcoding to measure insect diversity.
The results showed that weather had different effects on insect diversity depending on the region and the type of agricultural practice.
In general, insect diversity was higher in organic and recently transformed farmland than in conventional farmland, indicating that organic farming can enhance insect diversity.
However, weather anomalies also influenced insect diversity differently across regions. For example, in some regions, dry and warm summers increased insect diversity, while in others, they decreased it.
The researchers suggested that this could be due to the availability of water resources and the composition of plant communities in different regions.
The researchers concluded that weather is not only a driver of insect decline but also a source of variation in insect diversity across regions and agricultural practices.
They recommended that future studies should consider regional differences and interactions between weather and other factors when assessing the effects of climate change on insect diversity.
Weather impacts ecosystem services provided by insects
The study also discussed the implications of weather effects on insect populations for ecosystem services provided by insects, such as pollination and decomposition. The researchers argued that weather anomalies can disrupt these services by affecting the abundance, diversity, and activity of insects that perform them.
For example, pollination services depend on the availability and synchrony of flowering plants and pollinators.
Weather anomalies can alter the phenology of both plants and insects, leading to mismatches between them.
This can reduce pollination success and crop yields. Similarly, decomposition services depend on the activity and diversity of soil-dwelling insects that break down organic matter.
Weather anomalies can affect soil moisture and temperature, which can influence the survival and reproduction of these insects. This can affect nutrient cycling and soil fertility.
The researchers warned that weather effects on ecosystem services provided by insects can have negative consequences for human well-being and food security.
They urged for more research on how weather affects these services and how they can be maintained or enhanced under changing climatic conditions
