What do we know about insect responses to global change? A review of meta-analyses on global change drivers

Global change is causing major declines in biodiversity, especially of
insects. Scientific interest in global change impacts on insects has
increased in recent years, resulting in many different meta-analyses
examining questions within this topic. We performed a comprehensive review
of meta-analyses examining effects of global change stressors on insects
to identify well-studied questions and gaps in our knowledge and
synthesize responses of insects to those stressors. We identified 75
meta-analyses that fit our scope, accounting for 905 meta-results, and
spanning 18 global change stressors. Our synthesis identified several
global change stressors that are relatively well-studied across insect
groups, such as agriculture, habitat degradation, and pesticide use.
Moreover, other global change stressors were found to be relatively
less-studied, highlighting areas that need more attention; for example,
very few meta-analyses considered the impacts of global warming, ozone,
light pollution, and interactive effects of multiple stressors on insects.
Most stressors are more associated with negative than positive effects on
insects, except for nutrient addition, ozone, and air pollution. Negative
effects accounted for the large majority of consequences on reproduction
responses, which may help explain recent insect declines. Additionally, we
found evidence for higher trophic levels being more negatively affected by
global change, and insects in aquatic habitats experiencing fewer negative
responses to stressors. Given these largely negative impacts of global
change on insects, we argue for the need for national and local policy
actions to monitor and actively conserve insect communities.