Apr 07 2020

Who Speaks for the Insects

Dr. Matt Hill is filling the role of the Lorax for insects. They are a critical part of our ecosystem, and they are experiencing a long term decline. I know there is a lot to worry about in our complex world, and insects may not immediately jump to near the top of the list, but they are important, and also an index of ecological change.

We are used to thinking of insects as pests, just as we are used to thinking of bacteria as germs that cause infections. But most species of bacteria or completely neutral when it comes to humans, and some are actually beneficial (even critical). The same is true for insects. Only a relatively small percentage are pests (which itself is a relative term), while most go about their lives indifferent to humanity. Some species are directly beneficial, like pollinators. Regardless of their relationship to humanity, insects are a critical part of the ecosystem. Insects have the largest biomass of all animals (although animals as a group are dwarfed by plants and to a lesser extent bacteria).

A 2019 study concluded that 40% of insect species were at risk of extinction over the next few decades. Other studies show a significant decrease in insect biomass over the last 50 years. This is a loss of a critical source of food for the entire ecosystem.  Hill and his colleagues (Pedro Cardoso is first author) now have published a review of this research, warning the world of this critical decline, summarizing possible causes, and recommendations some steps individuals can take as partial solutions. They summarize the causes:

We are causing insect extinctions by driving habitat loss, degradation, and fragmentation, use of polluting and harmful substances, the spread of invasive species, global climate change, direct overexploitation, and co-extinction of species dependent on other species.

Like most stresses on the ecosystem, the biggest factor is land use. Recent estimates are that humans actively use almost half of all land on Earth, mostly for agriculture and ranges for domestic animals. Some of what is left is also “semi-natural”, meaning that it is not directly occupied or used, but is not “pristine” wilderness either. And of course the entire planet is now affected by things like pollution, climate change, and the introduction by human activity of invasive species. We are putting tremendous stress on ecosystems.

Some point out that ecosystems are resilient – they will survive, evolve, and adapt. That is true, but this happens on very long timescales. On human-relevant timescales, however, not so much. But also, even if life survives and adapts, there will still be a loss of biodisparity (using Gould’s term, and distinct from biodiversity). In the short term biodiversity, basically the number of different species and genetic populations within those species, is decreased but this can recover over time. Disparity, however, is a different concept – not just the amount of genetic diversity, but how different species are. To give a hypothetical example, if there were a mass extinction and dogs were the only mammals to survive, eventually they would evolve to fill every niche. Biodiversity would return. But all the mammals would be dog-like – biodisparity would never recover to its previous level.

From any perspective, we should be concerned about the relatively rapid transformation of the Earth’s surface and environment by humans and the impact this is having on the rest of life on Earth – including insects. Obviously the biggest things we do, like agriculture, have the biggest impact, and we do need to focus on how best to meet the growing needs of human nutrition with the smallest footprint. As an aside, this is not through organic farming, which because of its reduced yield and greater land requirements has a far worse footprint on the ecosystem. This is especially true since the more land we need for farming, the less and less efficient land we are spreading into. Conventional farming has serious issues as well, of course, including nitrogen runoff and the use of pesticides. We do need to find optimal science-based (not ideology-based) practices, and this is happening but is complicated by ideology. Perhaps our best tool is genetically modified crops – the one tool that short-sighted environmentalists are fighting.

The Cardoso paper also focuses on what individuals can do, pointing out some things that most people probably have never considered. There is considerable suburban sprawl in parts of the world, with includes a great deal of “seminatural” land. Here are their recommendations for individuals:

1. Avoid mowing your lawn frequently; let nature grow and feed insects

2. Plant native plants; many insects need only these to survive

3. Avoid pesticides; go organic, at least for your own backyard

4. Leave old trees, stumps and dead leaves alone; they are home to countless species

5. Build an insect hotel with small horizontal holes that can become their nests

6. Reduce your carbon footprint; this affects insects as much as other organisms

7. Support and volunteer in conservation organisations

8. Do not import or release living animals or plants into the wild that could harm native species

9. Be more aware of tiny creatures; always look on the small side of life.

Obsessively clearing downed trees and stumps may make our properties look nicer, but we are depriving the ecosystem of important resources. The insects that thrive in dead wood also feed other creatures, like woodpeckers. Also I think most people just pick the prettiest plants for their yard, without consideration of the local ecosystem. This is where local nurseries can play a role, advising their customers on how to have an attractive property but one that fits optimally with local wildlife. You can even put in plants that are particularly helpful to local insects. Even just knowing which weeds, like milkweed, to leave alone can be helpful.

We may need to make adjustments to town planning as well. This is where some higher-level decision-making is necessary. There are protections, for example, for wetlands. But perhaps we need protections for land found to be critical for insects and other wildlife. Collectively we need to be a little smarter in how we build our world to avoid unintended negative consequences on wildlife.

There are also some real issues that are at cross-purposes. We do need to control mosquito and tick populations that can spread disease, just as we need to control insects that are pests to our crops. We just need to find ways to accomplish this that don’t have indiscriminate negative effects on non-target insect species. It’s not going to be easy. There is no way to occupy half the planet with over 7 billion people and have a light footprint. But we can be a little smarter about it.

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