The people of New Zealand have cut so many trees that some native insects have lost their wings.
Within 750 years, humans have changed the natural landscape of the country’s South Island so much that scientists say it leads to rapid evolutionary changes in certain species.
Since no alpine forest can break the strong mountain winds, at least one species of insect has already left the aviation industry.
Zelandoperla fenestrata is a stonefly with two different phenotypes: one with wings that is able to fly; and one with stunted or no wings who is described as flightless.
The flightless stonefly is usually found at higher altitudes, where trees are scarce and strong winds can therefore easily blow a flying insect into the abyss. Meanwhile, the flyable flies are typically protected in alpine forests, where insects have to explore the entire habitat.
However, in regions where alpine forests have been cut down, researchers have found something fascinating. The insects at this altitude that can normally fly cannot.
It seems that man-made deforestation has indirectly stolen these insects’ ability to fly, and we have done so in a very short time evolutionarily.
Shortly after the arrival of the Māori, sometime after AD 1200, the extensive burning of native forests began, and now more than 40 percent of the forests that once covered New Zealand’s South Island have been turned into grasslands and fern bushes. Although this was the last major land mass developed by humans, we are already seeing the evolutionary impact on local wildlife.
The now flightless stonefly is probably just the tip of the iceberg.
“In addition to the local shifts derived here, it is likely that widespread deforestation has increased the percentage of flightless lineages in large parts of southern New Zealand,” the authors write.
The team fears that wingless stoneflies will not be able to search for partners in a larger area, increasing genetic diversity. This could potentially affect the health of the species and the risk of extinction of the insects in the long term.
In a rapidly changing world with so many other insects becoming extinct, this fear is not unfounded. By removing the forests that once sheltered stone flies, we are changing the way the wind blows.
The authors admit that there are likely factors other than wind that make insect flight on an open mountaintop unattractive – like habitat stability and temperature – but they argue that these strong gusts are the most noticeable feature of New Zealand’s mountaintops .
Charles Darwin would likely agree with this conclusion. More than a century and a half ago, Darwin and the botanist Joseph Hooker got into a heated debate about why so many insects can lose their wings when they are clearly such useful appendages.
On the islands between Antarctica and Australia, the two scientists found that almost all insects had lost their wings. Even the flies stopped flying.
Despite his colleague’s skepticism, Darwin claimed that the wind was to blame. If an insect tries to fly in such an open landscape, it will simply be swept out to sea. In this situation the flightless phenotype will always win.
In recent years his simple hypothesis has found more support. In 2020, for example, researchers found that wind played a large, if not exclusive, role in the loss of insect flight on remote islands in the Southern Ocean.
In the case of the New Zealand stonefly, the researchers suspect that the presence of water, the amount of light, or the productivity of the population can determine whether or not an insect population will fly.
In all likelihood, however, as Darwin once predicted, wind is blowing away all of these factors.
The study was published in Biology Letters.
