The errors of our ways
If you’re reading this, you belong to a handful of generations who have lived in a period of critical species loss. As discussed in a previous article, the severity and extent of the damage to biodiversity that we are currently witnessing may even equate to a 6th mass extinction. And, while we acknowledge – with increasing certainty – mankind’s agency in this alarming trend, the clock just keeps ticking.
In The Empathic Civilization, Jeremy Rifkin outlines the paradoxical relationship between empathy and entropy. That is, we are becoming better connected and more responsive to the needs of other humans. However, this growing awareness has been made possible by ever-greater consumption of the Earth’s resources.
This paradox can be borrowed or, in fact, extended. We know more and more about what it is about our behaviour that is damaging the planet, but can we act before we reach the point of no return? It’s a race against time and it’s scenario that can breed apathy and resignation. But, seen another way, it can also offer hope: if we got ourselves into this mess, maybe we can get ourselves out of it!
Although it’s clearly going to take more than a throwaway tagline to stem the tide, there’s a lot that we can do. And it starts by understanding the errors of our ways, whether it’s our untenable reliance on fossil fuels, reckless land management or negligent introduction of invasive species. We’ll leave the first two for another day; today, invasive species.
What makes a species invasive?
According to the Convention on Biological Diversity, “an invasive alien species (IAS) is a species that is established outside of its natural past or present distribution, whose introduction and/or spread threaten biological diversity”. In other words, this can be any form of biota (flora, fauna, fungi, etc.) that finds itself thriving somewhere it doesn’t belong and to the detriment of indigenous species.
However, don’t be misled the term ‘invasive’. Rather than invade a new territory, typically, invasive flora and fauna are either intentionally introduced or inadvertently transported to new lands by (you guessed it) humans! As we look at some examples, we’ll see that we’re often quick to vilify these ‘outsiders’, but rest assured, the blame invariably lies with us.
What’s the harm?
Ecosystems come in all shapes and sizes: from a minute drop of pond water to a vast savannah. They evolve over millions of years and represent the interconnectedness of living organisms and their world. A functional ecosystem is one with a balance between the four basic components: abiotic elements (e.g. water, air and minerals); producers (e.g. plants and algae); consumers (e.g. herbivores and carnivores); decomposers (e.g. earthworms and beetles).
To form a stable ecosystem species have evolved together. No better is this exemplified than by the development of symbiotic relationships, the phenomenon whereby unrelated organisms rely on one another for survival. So, when an alien species is thrown into the mix, this delicate balance is disrupted and the effects can be devastating. In fact, an analysis of the IUCN Red List shows that IAS are the second most common threat associated with species that have gone completely extinct.
The introduction of a non-native species can impact on an ecosystem in a range of ways, affecting indigenous species both directly and indirectly. Here are just a few examples:
Pythons on the run
When the ‘invader’ is a predator, the effects on the unassuming local fauna are predictably direct. Florida, for example, has experienced an invasion of Burmese pythons over the last couple of decades. The reason? Hurricane Andrew. No, the pythons weren’t blown over from South East Asia. The pythons were already in Florida – some in a zoo, others in a breeding facility. The 1992 hurricane damaged both of these structures and the runaway snakes wasted no time in populating the nearby Everglades. They adapted quickly to their new surroundings, preying on rabbits, opossums, foxes, deer, even coyotes and alligators. Today, in areas where pythons are well-established, many of these species are in decline.
As beautiful as their spring bloom may be, the spread of rhododendrons in the UK is a real cause for concern. The rhododendrons was brought over from Spain or Portugal at the end of the 18th century for use in botanical gardens and rich estates. It now covers nearly 100,000 hectares of land across Britain. Characteristic of invasive species, the rhododendron is fast-growing and harmful. Each plant can produce more than one million tiny seeds every year and, once established, they are very difficult to eradicate. Their thick vegetation block out the sun, their leaves are toxic to animals and many bushes carry a tree disease, called sudden oak death.
There is only one indigenous species of squirrel in Britain, the red squirrel. It seems that for the Victorians this was simply unacceptable. For in the 1870s they decided to introduce the exotic, North American grey squirrel to a park in Cheshire. In their defence, they were completely unaware of the risk this posed. The Victorians just liked collecting things. Grey squirrels don’t kill red squirrels, but they do compete for territory and food. They are considerably larger and more aggressive than red squirrels, so when they cross paths there is very little competition. Grey squirrels are also prolific breeders, producing up to 14 young a year. If this wasn’t enough of an advantage, grey squirrels carry the squirrel parapox virus. Fortunately for them, they don’t seem to be seriously affected by it, but it often kills red squirrels. The resulting situation is one of complete dominance. According to the Woodland Trust, the red squirrel population in the UK is down from 3.5 million to around 150,000. To put that into perspective, there are approximately 66 greys for every one red.
If you enjoyed reading about invasive species, keep an eye out for the next article.
We’ll be taking a look at some of the conservation strategies being used to combat this problem, as well as some practical ways that you help!