6. Making a summary

Pick out five key sentences and use them to make a summary of the whole passage.

7.Retell the text using the words and expressions from exercise 3 and the phrases given below

Firstly,…

The discipline seeks to understand….

Now in addition to…

As well as…

Thus,…

Unit 4

Global Warming Increases Eutrophication.

1. Skimming

Read quickly and get the gist of a passage. Do not try to understand every word; just try to get a general idea. Choose a new title for the passage, from this list:

(a) Increasing emissions of CO2

(b) Greenhouse effect on eutrophication

(c) Impacts on natural ecosystems

(d) The flux of nitrogen from soil

(e) Increased temperature influences decomposition rates

(f) How long eutrophication will last

Human activities may result in increased global warming during the next century due to increasing emissions of C0₂ and other greenhouse gases, such as CH₄, N₂0, and chlorofluorocarbons. Numerical models of the global climate predict an increase in global mean temperature of between 1.5 and 4.5 "C, and for Fennoscandia an increase in mean annual temperature of 3-5 "C. It is expected to result in both increased and reduced amounts of precipitation, depending on world region. In northern Europe, including the Baltic Sea area, increased amounts of water may be available for surface water and runoff. These changes are expected to have a number of impacts, e.g., on geomorphological processes, natural ecosystems, agriculture, forestry, and on water resources.

Important effects of increasing atmospheric CO₂ content on plants may be increasing photosynthetic rates, productivity rates and water use efficiency. However, growth limiting factors are supposed to appear.

Increased greenhouse warming will extend the growing season which will probably result in higher crop yields and forest production. The basically N-limited forest ecosystems may already be stimulated by the elevated load of atmospheric N. This trend may continue into the next century as well. Increased temperature will also speed up the decomposition and mineralization rates of the increased organic matter produced, resulting ultimately in increased amounts of available nutrients and humic material.

Atmospheric nitrogen deposition on large parts of southern Scandinavia is currently 10-20 kg per ha and year. Most of this deposition is thought to retain in terrestrial ecosystems, but in recent years these systems appear to have become "saturated" with nitrogen. With this occurring, an increasing release of nitrogen may be expected, resulting in increased flux of nitrogen from soil to inland surface waters and ultimately to marine areas. This loading is believed to continue into the next century as well.

The possible effects of an increasing greenhouse impact on eutrophication may be described through a number of processes coupled in series. An evaluation of the implications of climatic change for nutrient loading on Norwegian waters demonstrated, among other things, that if nitrogen saturation and mineralization of soil organic nitrogen increase, the future nitrogen loading on marine ecosystems could increase by 2-3 times. Thus, global warming is likely to increase nutrient flux to surface waters, including the Baltic Sea, and thereby stimulate an increase in eutrophication.