Why it’s time to reconsider the ecological contribution of introduced species – even in New Zealand
The loss of biodiversity is one of the most catastrophic developments of our time. The impacts may be get ahead of those of global warming.
Growing evidence that humans have triggered a sixth global mass extinction means that the protection of the remaining species is a unquestionable priority to ensure ecological services such as the carbon cycle, clean water and air, and healthy oceans.
The main factors of species loss are climate change, habitat degradation, Pollution, and alien species that become invasive. This has led conservation ecologists to follow the simple rule of “protect the natives, fight the aliens”.
If we had an unlimited budget, I would hardly dispute this point of view. But in a world where natural ecosystems face many other global changes aside from the loss of species, I think we should reconsider the ecological role played by exotic species.
Ecosystem function on the mixture of species
It could be argued that ecosystems are inherently so complex that we can never appreciate the exact contribution of an individual species, and therefore native species must be protected at all costs.
But this argument can be reversed. In many cases, alien species do not harm communities of resident species. It is only when an alien species becomes invasive that significant harm occurs.
The deliberate spread of species has been an integral part of human evolution for thousands of years. Many economically important plant species are exotic to most places, but they provide food for our growing population.
In a physically highly connected world, the involuntary displacement of land and marine species has now also become inevitable.
In some cases, introduced species can even complement native ecosystems. New world succulents are now an integral part of the Mediterranean landscape, without harm the local flora.
Sometimes introduced species perform ecological functions similar to those which are (or have been) performed by the natives. For example, European gorse stabilizes the coastal slopes in New Zealand, providing a local plant nursery.
In a particularly spectacular case, extinct turtles were intentionally replaced by an exotic species by “assisted colonization”. He seems to have work.
However, earlier and much less scientifically founded attempts at assisted colonization, such as the deliberate introduction of toads into tropical northeast Australia, has gone terribly wrong.
The bias of human perception
Humanity depends on many ecosystem services: clean water, the carbon cycle, elimination of pollutants and excessive nutrient loads, mitigation of global warming through the sequestration of terrestrial and marine carbon, prevention of erosion, and so on. name a few.
Preserving native species is one way to ensure these services for future generations. An ecological function-centered approach balances the cost of protecting native people and controlling alien species against the role of new assemblages of species shaped by human intervention.
At roughly equal cost, should we favor the addition of a breeding pair of a rare bird to the reforestation of several hectares of land? Such decisions are often difficult and must be based on the available science.
Obviously, there may be other reasons – cultural or aesthetic values for example – to protect native species, beyond the provision of ecosystem services. But people seem biased by what they’re used to.
For example, Switzerland provides generous grants to farmers for maintaining scenic alpine meadows, even though the native vegetation before human intervention was a much less biologically diverse alpine forest.
In Central Europe, the recently introduced tree of heaven (Ailanthus altissima) has triggered considerable efforts to eradicate it, while the European chestnut (Castanea sativa), introduced by the Greeks and Romans around 2000 years ago, is much appreciated and liked protection and even reforestation programs.
The above examples illustrate why we might need a more sober approach focused on ecological function to effectively protect our remaining natural treasures and the ecosystem services they provide.
The milestones in the evolution of life did not depend on individual species or assemblages of species, but on the emergence of new functional traits such as photosynthesis, predation or flight. Likewise, humanity ultimately depends on functioning ecosystems, regardless of the species that provide them.
/ Courtesy of Conversation. This material from the original organization / authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the authors.