Text 10. Climate, microclimate and forest

Microclimate is climate upon a small space. Thus we speak about the microclimate of the room you live in, of the class-room you study in, of the soil in your garden, the microclimate of this forest or of this or that part of the forest, etc. The kind of forest, its growth, its life are influenced both by climate and by microclimate. Various climatic zones give rise to principally different forests – the jungles in the tropics, the treeless poor vegetation in the Arctic, and green varied forests of the temperate climatic zone.

Microclimate influences the forest environment within a very small area and the changes in the structure of the forest cause changes in its microclimate. For example, when a road is built in an old or middle-aged forest many trees of the dense stand are to be removed and a gap is formed. As the observation shows, radical changes in the microclimate of the place where the gap is formed in comparison with the whole forest take place: thanks to the influence of direct solar radiation, the temperature of the soil and the air of the gap raises increasingly against the temperature of the soil and air of the whole forest. Changes in microclimate are in direct proportion to the width of the road and to the height of trees, and depend on the direction of the road too. The microclimate of some forest stands is less influenced by road building, of others – more. That is why all forest road building should be carried out cautiously.

To know the microclimate of this or that part of the area is important for cultivating crops in correct places, where they can grow and produce best.

Text 11. CfCs and ozone depletion

The use of CFCs is the main cause of depletion of the protective ozone layer. When the ozone layer thins, ultraviolet rays penetrate to the Earth's surface. This increases the risk of skin cancer in man – and damages animals and plants. Five to ten percent of the ozone layer over Denmark has been depleted. Over the South Pole, depletion exceeding 50% has been measured. In this case one refers to a hole in the ozone layer.

CFCs have been used, among other things, as coolants in refrigerators and freezers, and as propellants and solvents in aerosol sprays.

The majority of the countries in the world have entered into an agreement – the Montreal Protocol – which prohibits the use of CFCs from the end of 1995. Denmark and the EU countries have committed themselves to phase out use from January 1 this year. Product manufacturers have to a great extent found substitutes for the CFCs.

It can already be seen that the atmospheric content of CFCs has ceased increasing markedly. For the time being the level has stabilized.

Text 12. Controlling urban smog

In October 1991, the governors of nine Eastern states and the mayor of Washington, D.C., agreed to adopt smog control measures similar to those previously enacted by the state of California. The measures will require cleaner emissions from gasoline-powered vehicles and the introduction of cars powered by alternative fuels such as methanol.

A December 1991 report by the U.S. National Research Council (NRC) noted that despite two decades of massive and costly efforts, many areas ot the country have made little progress in reducing ground-level ozone. The major problem, according to the NRC report, is that flawed measuring methods underestimated the amount of volatile organic compounds in the atmosphere. Most ozone-control efforts have concentrated on reducing volatile organic compounds. Control methods have thus been less effective than anticipated.

The NRC said that in many regions, nitrogen oxides may also play a more important role than previously thought in ozone formation. Control of nitrogen oxide emissions may thus reduce ground-level ozone more effectively, according to the NRC.