The last 10,000 years have seen a fairly nice stable climate on Earth, during which the human race has expanded from one million to 7000 millions. This period is called the Holocene. We are now entering the Anthropocene, which due to humans will not be so comfortable. The “New scientist” of 27.02.2010 reported on a conference of 28 environment experts, concerning how close we are to ruining things completely. Besides climate, they considered eight other aspects. The following is a summary of their tentative conclusions, with some comments from me. It starts with the only positive case and finishes with the most urgent.
The stratospheric ozone level is about 5% better than we need to prevent serious radiation damage, and is improving. The situation was saved just in time.
When the oceans get too acid, animals will not be able to form shells, and will die. This affects corals, and many other animals of various sizes. Atmospheric CO2 affects this. Some seas may reach this stage by 2050. It is hard to say just how terrible the effect will be.
World-wide, about two thirds of available fresh water is being “used”. Most of the rest will be needed by 2050, because of population growth. Climate change may well reduce precipitation.
I understand that the main use is for agriculture. We shall have to change our food (e.g. less meat, crops that need less water), or eliminate population growth.
The annual extinction rate is at least 100 per million species. We need to get it down to 10 per million. The current rate of extinction is similar to that during the 5 or 6 earlier mass extinctions since life on earth began. It will get worse if the climate heats up. Biotopes with few species tend to be unstable.
The target rate is highly arbitrary. This is the aspect where we are furthest beyond the target, and the one where we know least about the effect on mankind. I see biodiversity as an ethic in its own right, alongside pro-human ethic. If, as seems likely, mankind wipes itself out, biodiversity will be needed to restart evolution towards intelligence.
Too much fertiliser in the water causes a bloom of simple organisms. When they die, their decomposition takes oxygen out of the water, leaving it stinking and “dead”. This has already happened to some lakes and rivers; the Baltic and Mediterranean are endangered. Too much nitrate in the soil is similarly bad. Nitrates also contribute to acid oceans. A century ago, German scientists developed a process for producing nitrate from air. Three or four times as much nitrate is being produced as can be recycled. How long can this go on, before the oceans are seriously affected? We can hardly reduce use of fertilisers, while still feeding the world.
I think this may remain only a local problem. With so much nitrate in the oceans, will not organisms develop that use it as a source of oxygen? Genetic engineering may help. The oceans should be farmed better as a potential source of much more food and fuel than the land. The plants and animals involved must be kept near the surface, and their salt content needs to be reduced somehow. Many of the small animals near the start of the food chain have shells that will be affected by acidity (see above). Why is so little being written about all this? Is anybody working on it?
Phosphate fertilisers produce local problems similarly to nitrate. The quantities are much less, due to the availability and cost, and can be recycled at present.
I think recycling takes place largely due to fishing by humans and birds.
Of land that is not snow covered, 12% is used for agriculture. This should not go above 15%. But it will probably reach this value by 2050.
I was surprised how low these figures are. Of course a lot of land is desert, which is no use without (fresh) water, (see above). Other land is just rock. Erosion, pollution and rising see levels are reducing fertile land. Continental drift very gradually converts the muck under the oceans into land. Before agriculture started, this balanced erosion. Can we restore the balance in the next few hundred years?
The atmosphere in some parts of the world is full of unhealthy aerosols. They cause millions of human deaths pro year. It is unclear how bad this will/can get.
About 100,000 chemical substances are produced and used. Production and use of these generate many further compounds. Some of these may be responsible for various serious diseases.
Obviously some of the worst cases are known (DDT, dioxin). Population control would not be a problem if many others had terrible effects. I think there is no great general problem. But there is a constant slight chance of a new substance wiping out mankind. Why did most dinosaurs die out while mammals survived? Genetic engineering is the main danger, although only a small one.
“This is the big one”. Atmospheric CO2 is already 10% above the “safe” limit and is increasing! The trouble is that there is delayed positive feedback; we do not know how strong. Melting Arctic pack-ice will reduce the Earth’s albedo. Warming tundra will release the greenhouse gas methane. Atmospheric water-vapour, another greenhouse gas, will increase.
This committee avoids a concrete prediction, but they seem to fear a 6 degree temperature rise by 2100. This would have dramatic effects.
I believe it would be possible to support the current Earth population level for the next hundred years, but I do not believe it will happen! As well as the above problems, remember how many countries have nuclear weapons.