Your individual yard might assist reverse world insect declines

The headlines about the “Insect Armageddon” are constantly being published, and seemingly endless studies focused on the global decline in insect populations are being written.

There were some staggering numbers, like the 2017 study from Germany, which showed a 75% decrease in flying insects in protected areas over 23 years. This was followed by another, widely published study in which bird species in North America were estimated to have declined by 29% since 1970. It would be foolhardy to deny the connection, since insects are an important source of food for many birds.

These numbers are enough to make anyone feel powerless in the face of the many environmental challenges we face. Climate change, habitat loss and the increased use of pesticides all contribute to what the ecologist David Wagner calls “death by a thousand cuts”. However, there is evidence that in helping insects and other wildlife populations through individual action we can have a significant impact by simply planting more native plants in our own yards and gardens.

In a review article published in Ecological Entomology, researchers combed existing scientific evidence on the role of alien plant species in insect decline – a factor that is often overlooked. Humans have purposely and accidentally introduced new plant species far and wide. In fact, an estimated 13,000 plant species have been introduced outside of their natural range due to human activity.

Hitchhiking along with these plants are often their pests, which can devastate species that haven’t developed defenses for them – just think of the massive effects of chestnut rot that came with imported Chinese chestnut trees. American chestnut trees and the insects that specialize in them are not only functionally extinct, but more than 70 million kilometers of forests in the eastern United States have been completely changed in less than 40 years.

Invasive plants, widely seen as a threat to biodiversity and ecosystem function, are crowding out native plants and the species that depend on them. Because native plants evolved within a particular ecosystem, their long evolutionary history has made them paired with numerous other species that rely on them to survive. For example, around 70 percent of all known caterpillar species develop on just one plant family.

As a result of this coevolution, many species of insects became specialists, relying on certain plants for food and for laying their eggs. The chemistry of the foliage, the time of year the plant grows and blooms, the physical shape of the leaves and flowers, and the way these things coincide with the life cycle of the insect are important factors in coevolution.

Some non-native plants not only crowd out native species, but even act as “ecological traps”. This causes insects to lay their eggs on a plant that does not support larval development. Monarch butterflies looking for milkweed to feed their young have been fatally tricked by one such alien plant that spreads in the eastern United States

“… even if we see green spaces, it is green spaces that are not ecologically functional.”

If you know what we are doing now to address the damage caused by invasive plants, you may be surprised to hear that 50 to 70 percent was intentionally introduced for landscaping purposes. While land managers work tirelessly to restore native habitats through control and removal, nurseries continue to sell the same species even if they are on the do not plant list. This means that it is just a small breeze or other seed dispersal event that does not return to restored areas.

Desiree Narango, an ecologist at the University of Massachusetts, Amherst and co-author of the review study, suggests that in addition to planting native plants, you can have a particularly powerful influence on which species are most productive for supporting insect diversity in your area. In the eastern United States, for example, one of the best things you can do is plant an oak tree as it supports a large number of caterpillar species, which in turn support bird species. The Xerces Society has a collection of plant lists that you can use to make informed decisions.

With bird watching growing in popularity while people are spending more time at home than ever before, one of the best things you can do for birds is building a natural bird feeder by planting native plants. This will support all of the warblers, tanagers, orioles, and other species that will not use your hanging bird feeder but will be attracted to the insects in your yard. It can even protect them from the spread of diseases that can appear in traditional bird feeders.

Surprisingly, some of the ongoing landscape sustainability efforts in the western US, which often push for drought tolerant crops and lawn removal, do not emphasize native plantings in their efforts. Narango describes the investigation of shipyards in LA that were rated “Wildlife Friendly” by the National Wildlife Federation to determine that all plants were not native. “There’s this urge to plant drought tolerant crops and the horticultural industry has responded by importing massive amounts of South African succulents … and so we’re actually getting an increase in alien plants and potentially invasive plants in these arid systems.” This is particularly worrying given that the US Southwest supports some of the highest wild bee diversity in the country, but most of these bees are pollen specialists. Without the plants to support them, the bees cannot survive.

Jessica Bolser / USFWS via Wikimedia Commons

Fortunately, there are native plant societies out there that can assist you in your efforts to build insect-friendly yards, like these lists of native nurseries from the California Native Plant Society and Plant Native. The Audubon Society also has an initiative to help you find the native plants that will best support birds in your area.

Realistically, increasing the effects of insects can be difficult – they are not the kind of charismatic animal that evokes strong emotions in most people. However, the loss of insects has cascading effects on our lives and ecosystems. They not only form the basis for food webs and support the animal world, but are also required for pollination, including for agricultural crops. Given the many impacts we have on them, we are one step closer to managing our negative impacts on biodiversity.

With non-native plants replacing native habitats on a global scale, it is difficult to measure the magnitude of the impact on insect decline. In urban areas, agriculture, forestry and horticulture must be taken into account, which together represent massive changes in the habitat of insects. Planted forests may superficially resemble healthy habitats, but at least 25 percent of them are made up of non-native tree species – consider the pace of expansion of oil palm plantations, for example a plant native to Africa that now covers expanses of Asia and Central and South America .

Narango points out, “When you think of habitat loss, the alien plants … that loss only annoy. Even when we see green spaces, those green spaces are not ecologically viable.”

Despite all of the many challenges, Narango is optimistic about what we can do with this information. “When the conversation about insect decline comes up, we hear a lot about habitat loss, climate change, artificial light and pesticides, and some of those more direct effects, and there’s a lot less room in talking about non-native plants. And the thing about plants is that it can be done! Tackling climate change is a big problem, a big job. But planting things is something anyone can do when we are armed with the information. “

Narango: “In addition to planting native plant species, there are always many other really simple things you can do, like reducing the amount you mow to help bees, reducing or eliminating pesticides, reducing or eliminating your lawn and really fair, paying attention to what is out there can be a really eye-opening experience and help you make the decisions you make and how to maintain a garden that is not just plants but plants as well Includes animals. ”