Loss of biodiversity means the number of different species in a particular habitat has fallen. If the missing species still live elsewhere maybe they can be re-introduced. However, if a species has a limited distribution, falling numbers usually means they are headed for extinction, like the dodo and the Tasmania tiger.
So, the first stage in loss of biodiversity is the falling number of species. This may be caused by some non-human factor, but in recent years mostly it is human interference. As anyone over the age of 70 can testify, the variety and abundance of wild creatures has been falling. For example, when did you last see Christmas beetles or the large ‘greengrocer’ cicadas capable of making a noisy racket in summer? Or such insect-eaters as willy wagtails, mudlarks, swallows and lizards, once present in noticeable numbers. These species are not extinct yet, but if they keep being squeezed out of suitable habitats, they will end up endangered and on their way to extinction.
Biodiversity matters because healthy and viable ecosystems are maintained by an interdependent web of diverse species. In healthy ecosystems, the population of each species goes up and down over time, mostly within a limited range. However, when a number keep climbing, that species is usually headed for an environmental collapse. The dynamic interactions of all the different species keep that ecosystem in balance and, in general, the greater the number of different species the more stable the ecosystem.
However, if humans over-exploit a selected species within an ecosystem, this can lead to a population collapse. A famous example is the overfishing of cod on the Newfoundland Banks. When those fisheries collapsed in 1992, 40,000 people who made a living from cod and associated activities lost their livelihood. Around the world, there are many examples of overfishing, which have had devastating effects on species such as dolphins, penguins and seabirds that rely on fish for food.
Australia’s first people did a good job of being part of the ecosystems where they lived. They moved around their home country to take advantage of seasonal abundance and understood the need not to over-exploit. However, since white settlement, this ancient continent has been over-exploited, causing the extinction of many species. This has come about through deforestation, and poor water and land management, leading to salination and desertification. The recent mass fish deaths on the Darling River and Menindee lakes can be largely attributed to human over use of water under drought conditions. So, any aquatic birds that relied on those fish for food will now be starving and not breeding.
Maintaining balanced ecosystems and maximum biodiversity has never been a priority for humans; because for most of our existence—nearly 200,000 years—our numbers were relatively small. Now, through a population explosion in human numbers—now over 7 billion—we are using far more resources and endangering or causing the extinction of many species—hence the loss of biodiversity.
While the loss of large animals is well reported, a recent drop in insect numbers by 40 per cent has drawn little media attention. Such a fall in insect numbers may not seem concerning if you think in terms of fewer pesky flies and less chance of been bitten by a mosquito. However, if you consider that honey bee numbers are also falling and they are necessary for pollination, then more people should start listening. Many food crops need honey bees as pollinators to trigger the growth of nuts, seeds and fruit.
In summary, loss of biodiversity unbalances the interactions that maintain the viability of ecosystem and is associated with a massive wave of recent extinction. Eventually, the plants and animals humans rely on for food, clothing, etc., may cease to be viable species in the absence of a multitude of other organisms they have evolved to interact with. Furthermore, the world is a greatly diminished place in the absence of so many beautiful and unique species.
Reproduced from Victorian Humanist, Vol. 58, No. 2, Mar 2019
Copyright © 2019 Rosslyn Ives