What is it about?
Many headlines claim that losing plant species will inevitably lead to mass insect extinctions, but surprisingly, there’s little scientific evidence for this. We tested this idea using a massive dataset of plant-insect interactions and long-term population trends for 3,429 plant species and 2,239 insect species in Germany—including pollinators like bees and hoverflies, as well as herbivores like butterflies, moths, and sawflies. We found that insect populations do tend to decline when their host plants decline. But the relationship isn’t as simple as "fewer plants = fewer insects." When we simulated the extinction of all currently threatened plants, 96% of insect species still had access to at least 25% of their usual host plants. And almost all of them (98%) still had at least one widespread plant in their interaction portfolio. Even highly specialized insects often rely on non-threatened plants. For example, the Viper’s Bugloss Mason Bee (Osmia adunca) depends entirely on viper’s bugloss (Echium vulgare)—but since this plant is common and not at risk, the bee is not in direct danger from contemporary plant diversity loss. We also identified the key plant species that support insect diversity, especially threatened insects. In the case of bees, for example, just six plants—bird’s-foot trefoil (Lotus corniculatus), charlock mustard (Sinapis arvensis), greater knapweed (Centaurea scabiosa), harebell (Campanula rotundifolia), wild carrot (Daucus carota), and viper’s bugloss (Echium vulgare)—alone provide support for 56% of all threatened bee species. Our results show that while plant declines do contribute to insect declines, the extinction of threatened plants is unlikely to trigger a catastrophic extinction wave of insects. Instead of focusing only on preventing plant extinctions, conservation efforts should also prioritize keeping such key plant species abundant in the landscape.
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Photo by Josephine Amalie Paysen on Unsplash
Why is it important?
Many headlines suggest that losing plant species will cause mass insect extinctions, but the reality is more complex. Our study provides much-needed data to clarify this issue. While insect populations do decline when their host plants disappear, most insect species can still find alternative plants to survive—even when threatened plants go extinct. This is good news for biodiversity, but it also means conservation efforts need to focus on more than just preventing plant extinctions. Our research identifies key plant species that support insect diversity, especially for threatened insects. By keeping these plants abundant in the landscape, we can help safeguard insect populations even as some plant species decline.
Perspectives
When we first started looking into the relationship between plant and insect declines, we expected to find a clear-cut pattern—fewer plants leading directly to fewer insects. But the data told a more nuanced story. Yes, insects are affected when their host plants disappear, but nature is often more resilient than we assume. Many species, even highly specialized ones, have backup options that help them survive. For me, the biggest takeaway is that conservation needs to be both strategic and holistic. Whilst promoting threatened plant species is important in its own right and can support insect diversity, it’s not just about saving rare plants—it’s about ensuring that key plants remain abundant. This, however, may be more challenging than it seems. Some research suggests that even these currently common plants are declining, and how they will respond to climate change remains an open question.
Dr. Ingmar R. Staude
Universitat Leipzig
Read the Original
This page is a summary of: Insects decline with host plants but coextinctions may be limited, Proceedings of the National Academy of Sciences, October 2024, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2417408121.
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