Disasters such as earthquakes, tsunamis, volcanoes, floods, oil spills and radioactive fallout cause massive death of people, pigs, bats and birds. These disasters also impact the immune health of survivors. All harbor viruses.
Plants with leaves no more efficient than today's solar cells could out-compete real plants, crowding the biosphere with an inedible foliage. Tough omnivorous bacteria could out-compete real bacteria: They could spread like blowing pollen, replicate swiftly, and reduce the biosphere to dust in a matter of days. Dangerous replicators could easily be too tough, small, and rapidly spreading to stop - at least if we make no preparation. We have trouble enough controlling viruses and fruit flies.
Humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.
Carbon dioxide pollution is transforming the chemistry of the ocean, rapidly making the water more acidic. In decades, rising ocean acidity may challenge life on a scale that has not occurred for tens of millions of years. So we confront an urgent choice: to move beyond fossil fuels or to risk turning the ocean into a sea of weeds.
We're dabbling in eugenics all the time, breeding ideal crops to replace less aesthetic or nutritious or hardy varieties; leveling forests to graze cattle or erect shopping malls and condos; planting groves of a few familiar trees that homeowners and industries prefer.
Man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords.
There is hardly a place on Earth where people do not log, pave, spray, drain, flood, graze, fish, plow, burn, drill, spill or dump. There is no life zone, with the possible exception of the deep ocean, that we are not degrading.
One thought that occurs to me is that men will continue to withdraw from nature in order to create an environment that will suit them better.
Natural capital is easy to overlook because it is the pond we swim in. One can live perfectly well without ever giving a thought to the sulfur cycle or wetland functions. Only when the benefits nature provides are disrupted do we take notice.
Canada, as you know, is a major important nation boasting a sophisticated, cosmopolitan culture that was tragically destroyed last week by beavers.
So you can imagine what happens when a mainland species gets introduced to an island. It would be like introducing Al Capone, Genghis Khan and Rupert Murdoch into the Isle of Wight - the locals wouldn't stand a chance.
Humans are upsetting a fragile balance that their own human ancestors established.
If you cut down the forest, you know what happens: The whole of Asia turns into a desert. Without water, you're talking civil unrest, war, mud slides - the whole bloody lot.
If you take away the predators in the prairies and the national parks, you suddenly have an explosion of elk, and then you have a lack of the food source for the elk, so they strip all the ground bare and that takes away the cover, on and on and on and on. The whole food chain is disrupted.
From a scientific perspective there is some indication that a nuclear war could deplete the earth's ozone layer or, less likely, could bring on a new Ice Age - but there is no suggestion that either the created order or mankind would be destroyed in the process.
While ants exist in just the right numbers for the rest of the living world, humans have become too numerous. If we were to vanish today, the land environment would return to the fertile balance that existed before the human population explosion. Only a dozen or so species, among which are the crab louse and a mite that lives in the oil glands of our foreheads, depend on us entirely. But if ants were to disappear, tens of thousands of other plants and animal species would perish also, simplifying and weakening land ecosystems almost everywhere.
Seasonally ploughing and harvesting crops will mash up a few moles, slice through a burrow of field mice and crush any ground-nesting bird chicks. Far more significant, however, is the creation of the field in the first place: an act that replaces entire ecosystems, along with all their animal inhabitants.
When we conduct agriculture, we are, therefore, altering the ecological arrangement that was responsible for our genesis as a species. I think that this is the reason that this alienation has allowed us to see and regard land mostly as a resource. So we have created a problem for ourselves from the word "go," for land is not a resource any more than humans are resources.
The great ecosystems are like complex tapestries - a million complicated threads, interwoven, make up the whole picture. Nature can cope with small rents in the fabric; it can even, after a time, cope with major disasters like floods, fires, and earthquakes. What nature cannot cope with is the steady undermining of its fabric by the activities of man.
Nile perch is a fish that was introduced into Lake Victoria. The reason that fish was introduced into Lake Victoria was because it was decided that the people living near the lake needed more proteins than they were getting.
Several times in Earth's history, rapid global warming occurred, apparently spurred by amplifying feedbacks. In each case, more than half of plant and animal species became extinct. New species came into being over tens and hundreds of thousands of years. But these are time scales and generations that we cannot imagine.
Perhaps the simplest example is a synthetic plastic, which unlike natural materials, is not degraded by biological decay. It therefore persists as rubbish or is burned-in both cases causing pollution. In the same way, a substance such as DDT or lead, which plays no role in the chemistry of life and interferes with the actions of substances that do, is bound to cause ecological damage if sufficiently concentrated.
Our planetary system is affected by a magnitude of force as powerful as any naturally occurring global catastrophe, but one caused solely by a single species: us.
If enough species are extinguished, will the ecosystems collapse, and will the extinction of most other species follow soon afterward? The only answer anyone can give is: possibly. By the time we find out, however, it might be too late. One planet, one experiment.
We accept it as normal that people who have never been on the land, who have no history or connection to the country, may legally secure the right to come in and, by the very nature of their enterprises, leave in their wake a cultural and physical landscape utterly transformed and desecrated. What's more, in granting such mining concessions, often initially for trivial sums to speculators from distant cities, companies cobbled together with less history than my dog, the government places no cultural or market value on the land itself.
