Here is a review of a new book about the biosphere. It looks at the complex interactions of biosystems and leaves me with the impression that environmentalists who shout that we are killing our future are jumping to conclusions. An excerpt:
As a result of the burning of coal and oil, the driving of cars, and other human activities, the carbon dioxide in the atmosphere is increasing at a rate of about half a percent per year.
Everyone agrees that the increasing abundance of carbon dioxide has two important consequences. First, carbon dioxide is a greenhouse gas, transparent to sunlight but partially opaque to the heat radiation that transports energy from the earth's surface into space. Second, carbon dioxide is an essential nutrient for plants on land and in the ocean. The increase in carbon dioxide causes changes, both in the transport of energy through the atmosphere and in the growth and reproduction of plants. Opinions differ on two crucial questions. Are the physical or the biological effects of carbon dioxide more important? Are the effects, either separately or together, beneficial or harmful?
The biological effects of carbon dioxide on plants can be seen in changes of rate of growth, ratio of roots to shoots, and water requirement, which are different for different species and may result in shifts of the ecological balance from one kind of plant community to another. Effects on plant communities will also cause effects on dependent communities of microbes and animals. Biological effects are difficult to measure but are likely to be large. Experiments in greenhouses with an atmosphere enriched in carbon dioxide show that the yields of many crop plants increase roughly with the square root of the carbon dioxide abundance. If this were true for the major crop plants grown in the open air, it would mean that the 30 percent increase in carbon dioxide produced by fossil fuel-burning over the last sixty years would have resulted in a 15 percent increase of the world's food supply.
The fundamental reason why carbon dioxide abundance in the atmosphere is critically important to biology is that there is so little of it. A field of corn growing in full sunlight in the middle of the day uses up all the carbon dioxide within a meter of the ground in about five minutes. If the air were not constantly stirred by convection currents and winds, the corn would not be able to grow. The total content of carbon dioxide in the atmosphere, if converted into biomass, would cover the surface of the continents to a depth of less than an inch. About a tenth of all the carbon dioxide in the atmosphere is actually converted into biomass every summer and given back to the atmosphere every fall. That is why the effects of fossil fuel-burning cannot be separated from the effects of plant growth and decay.
Read the whole thing. It's very interesting.
