The term “biodiversity” gets used a lot in modern conservation, though there seems to be some confusion as to what it actually means. Invasive biology proponents—those who believe that the invasive infiltration of non-indigenous species into an ecosystem inhibits the thrivability of indigenous ones—often assume “biodiversity” refers to just endemic populations in situ, something to be protected at all costs. In New Zealand, this is a big issue, and one of the key assumptions that is used to justify the “Predator Free New Zealand by 2050” movement.
|Awesome Poster by Pedro Teixeira|
The Oxford dictionary defines biodiversity as “the variety of plant and animal life in the world or in a particular habitat, a high level of which is usually considered to be important and desirable.” There is nothing in this definition about a species being endemic. And here’s why this matters: If a species exists, and perhaps even thrives, outside of its native natural habitat (and therefore might be considered an invasive species in another habitat), but it no longer thrives--or perhaps even exists--in its native habitat, is that a loss of biodiversity? If a plant or animal exists in a controlled environment but not in the wild, is that a loss of biodiversity? For more on this line of thinking, see my post on endangered species.
And while we’re on the subject of definitions, words like endemic and native are often wrongly used interchangeably, so just to clarify... Endemic refers to an indigenous species found naturally nowhere else on the planet. Native species, by contrast, are species that naturally occur in a place, and they also occur elsewhere. In New Zealand, for example, the kiwi and the tui (birds) are endemic, while fantails and pukekos (birds) are natives.
Some numbers: According to Wikipedia (they have a pretty decent article on biodiversity I think), 99.9% of all animals that have lived on this planet are extinct. The estimated current number of different species on earth ranges between 10 million and 1 trillion, of which a little over a million have been identified. Which means scientist haven’t really got a clue about how much biodiversity there really is on this planet. (I suspect the trillion figure may include micro-organisms.)
The earth has undergone five mass extinctions that we know about, and it is generally accepted that we are undergoing a sixth mass extinction now, a human-generated catastrophe caused primarily by habitat destruction. The World Wildlife Fund estimates the annual number of extinctions as between 200 and 100,000, while the UN Environment Program estimates 150-200 species become extinct daily. Such diverse numbers suggest nobody really has a clue. It is estimated between 5000 and 10,000 new species are discovered/identified every year.
In the 19th and 20th centuries, acclimatisation societies sought to increase biodiversity by introducing non-native species into newly-colonized lands. These societies were popular in the Americas, Australia, and New Zealand. Numerous birds and game species were introduced by settlers to make their new homes feel a bit more like their old homes, for farming purposes, and to provide wild meat and fish for the table and hunting and fishing pleasures.
Today there is a strong movement to reverse many of these deliberate introductions ostensibly because of a concern that introduced species puts the survivability of indigenous species at risk, though the actual risk from introduced species may be fairly small.
Ultimately, most scientists agree that the greatest threat to the planet’s biodiversity is humanity. We decimate wild ecosystems and habitats with our forest clearings, and our agriculture, our seas of plastics, and our toxic chemicals that contaminate our lands and our waterways, our seas and our skies. One recent study in Germany documents an astounding 75% decline in insects biomass in Germany over the past 30 years. We tend to walk carelessly across the surface of our planet with hobnail boots and are headless of our tread.
Some of my other posts on the conservation theme: