Colliding Forces: Climate Change, Land-Use, and Invasions Fuel Insect Loss
Gossner MM, Menzel F, Simons NK. 2023. Less overall, but more of the same: drivers of insect population trends lead to community homogenization. Biology Letters 19: 20230007. Open access article.
Summary
Insect populations are decreasing worldwide, both in abundance and diversity. This is a societal concern, as insects provide many services necessary for ecosystem function. Gossner et al. (2023) introduce and summarize a special issue in Biology Letters focused on global insect population declines. The authors identify three key drivers that affect insect communities: climate change, land-use change, and biological invasions. Climate change is particularly important because insects are highly sensitive to temperature, with a shift towards warm-adapted species and range contractions of cold-adapted species. Anthropogenic land-use changes can also negatively impact insect species, leading to less diverse communities and an overall decrease in biodiversity. Broadly, invasive species impact native insect populations through direct interactions, such as competition and predation, and through indirect interactions by changing abiotic conditions, like soil chemistry and access to sunlight. These drivers do not act in isolation, and their compounding effects can magnify their negative impacts. For instance, some aquatic invasive species colonize human structures and compete with native species, which are already vulnerable from decreased habitat quality. Additionally, climate change facilitates the spread and success of invasive species. While the loss of an insect species or a reduction in their population size may seem inconsequential, the ongoing decline has cascading effects within ecosystems.
Take home points
Insects are an immensely biodiverse group, with over 91,000 species described in the US (and likely a similar number of species that have not been described!). They provide ecosystem services that benefit habitats and humans.
Climate change, land use change, and invasive species across taxa are all major drivers of declining insect populations worldwide.
The interactions of climate change, land use change, and invasive species can magnify the negative effects on insect populations, threatening both biodiversity and ecosystem function combination of common garden experiments and experiments set up along environmental gradients.
Management implications
It is important to monitor insect populations at fine taxonomic levels (e.g., species or genera) to detect population declines or shifts in insect communities. By using new identification tools, such as Seek and iNaturalist, such monitoring efforts are more accessible to non-experts and present opportunities for community engagement.
In addition, it is important to monitor ecosystem functions that are affected by insects, such as pollination and decomposition. This can help identify key species that maintain healthy ecosystem functions. For example, native species that have generalist diets were found to be important for processes such as decomposition and nitrogen fixation (see Houadria & Menzel, 2017). Monitoring ecosystem function can also reveal impacts of invasive species on abiotic processes.
Promoting native plant diversity into management can help maintain a diversity of native insect species, as many insect species have specific plant hosts.
The time to take action is now: management interventions to support native insect populations include improving habitat connectivity to allow migration, integrative invasive pest management, and restoring critical habitats for priority native insect populations.
Keywords
Competitiveness; Native Insects; Land Use Change; Climate Change; Invasive Species