Human impact on natural areas can have drastic unintended circumstances. In fact, introduced or alien species are one of the leading drivers of the loss of biological diversity. Most famously, these losses are the result of the invading species outcompeting natives, who typically are naive to such pressures. Not all alien species take hold, of course, but very often the ones who do can do so in viral proportions. That’s why there are so many more English sparrows and European starlings in the cities of eastern North American than there are bluebirds. And why English ivy can be such a pervasive problem in the Pacific Northwest, where the climate is perfect for it to grow unchecked.
Many times, invasive species arrive in an ecosystem inadvertently. For example, the now infamous zebra mussel of Europe is literally choking out parts of the American Great Lakes and reeking ecological havoc, having arrived on the hull of giant cargo ships thirty years ago. However, quite often alien species are introduced with the best intentions. For instance, the eucalyptus trees of Australia are the fastest-growing trees in the world and were used widely throughout Africa in early reforestation programs and to create village woodlots to provide easier access to firewood. Naturally, in hindsight it’s clear that planting the fastest-growing anything where it doesn’t belong can only lead to problems, setting up a botanical race that few native plants can win.
Michael Samways is an entomologist at the University of Stellenbosch, and chair of the IUCN/SSC Invertebtate Conservation Subcommittee. As such, he is an expert on insect conservation, and is one of the scientists leading the charge to protect these often forgotten, but essential animals.
But conservation is rarely simple. As Dr. Samways explained, “South Africa has many rare and threatened endemic invertebrates. Among these are certain damselflies and dragonflies that are globally threatened, principally by invasive alien trees; two such species are the Cape bluet and Ceres stream damsel. Both of these species were thought to be extinct: The Ceres stream damsel had not been seen since 1920, while the Cape bluet had not been recorded since 1962. However, in 2004, both species were found inhabiting a small pool of standing water in the western Cape.”
The area had recently been cleared of invasive alien trees, including eucalyptus. Samways added, “This is the first time that such a recovery has been demonstrated and is a very positive and exciting development showing that removal of invasive trees can result in recovery of some natural species that were on the brink of extinction.”
Interestingly, what began as a public works program providing jobs in rural areas wound up helping the endangered dragonflies. A nationwide program launched to remove the eucalyptus not only helped local villages and farmers, but also increased those areas’ biodiversity.
The great thing about this restoration program is that while it had direct positive impacts on saving several threatened species, it also benefited humans with new jobs and better access to water for farming. That’s because the water-loving invasive trees had changed the hydrology in many regions, so their removal provides more water for birds, bugs, and farmers.
And since invasive species don’t disappear easily, the removal of any alien regrowth will provide jobs in the future as well.
The moral of the story is to leave the eucalyptus to the koalas and let the sun shine down on the South African dragonflies.
And for Dr. Samways, it isn’t just about bugs. He remains hopeful about the chances for overall ecological restoration. “We believe,” he said, “that with the right management, the veldt and the rivers of South Africa can be restored to their original condition.” And he remains practical as well, adding, “As a result of our studies, we have shown that increased agricultural production and biodiversity conservation need not be mutually exclusive.”
