Species losses: Not a mere scorecard, but the unravelling of Life
A crisis of species loss is building up around the world [http://theconversation.com/plundered-for-their-unique-body-parts-sawfish-are-on-the-brink-27743 ]. Biodiversity is under increasing pressure. What does this signify; what does it foreshadow?
Species come and go. The average tenure of each on Earth is around two million years. As they disappear or evolve their host ecosystem adapts; such changes are going on all the time.
Those changes, however, are mostly gradual, and ecosystems have time to adjust. Occasionally a 'big bang' extinction occurs, such as has happened at least five time in the last half billion years. Even so, those events -- which have wiped out between half and nine-tenths of all species -- have been spread over several thousands of years or longer, in response to various kinds of major and protracted convulsions in the planet's environment and climate. Given several million years of time, Life then regroups and occupies the vacant landscapes with a dazzling procession of new and novel species
We live now amidst the Sixth Extinction. Not only is this extinction of our own making, but it is occurring unusually rapidly, and accelerating, as humans occupy, change and impoverish more and more of Earth's terrestrial and marine landscapes. Australia's record is particularly bad; over half the mammals that existed here before Europeans arrived are now extinct. More of our animals are now on the danger list -- quolls, various frogs, rock wallabies, the Tasmanian devil, the pygmy possum, and others -- as rabbits, foxes, feral cats, cane toads, water buffalo and other invasive species proliferate. Similar lists apply offshore and within the plant kingdom ... and within CSIRO, where the research and documentation of Australia's biodiversity is also facing extinction, deemed by wanton and ignorant government to be a luxury item.
We wring our hands over the impending loss of many iconic species. But what is missing from most of our public discussion is what the loss of a species, or several species, portends for an ecosystem at large. And this is where our education and culture has so far failed to impart a bio-understanding of the intense inter-dependence and mutualism of life within an ecosystem. Indeed, that used to be the unadorned condition of our pre-agrarian ancestors, necessarily living within the limits of local food and water supplies, and being part of nature's kill-and-be-killed cycle. Today, though, most of us are many steps removed from those natural processes; hence, we are less aware that to eliminate sharks, as top predators, or to acidify the oceans and shrink the planktonic base of the marine food web is to trigger a cascade of change, loss and forfeited function throughout whole ecosystems.
Much of what we humans think of as the 'functions' of nature -- the recycling of nutrients, the cleansing of water, the pollination and healthy growth of edible plants, the constraints on infectious agent activity, and the buffering of coastlines by mangroves and dunes -- are manifestations of internal ecosystem activity that underpin the survival and reproduction of that system’s component species.
If we view today's precarious situation with biosensitive insight, we see that current human practices are not merely creating casualties on the sidelines as we trample on the environment in our march towards greater 'prosperity'. The elimination of species great and small, and of whole ecosystems (such as could happen with the Great Barrier Reef or parts of the Murray-Darling Basin under future drier conditions), is weakening Earth's life-support system. If the losses continue, then Healthy Life on a Healthy Planet becomes less attainable, or worse.