relative sensitivity of different regions to acidification-related impacts (Figure 8).
Although concentration on acidification in Asia has only recently begun, several
studies have indicated evidence for soil acidification in China that may be
associated with acidic deposition. Figure 8 shows that many ecosystems in NE
and SE Asia may be very sensitive and so the risks of acidification damage may be
rather high in areas with high deposition rates.
Eutrophication. Nitrogen deposition, either as ammonium or nitrate, can
eutrophy (nutrify to excess) terrestrial ecosystems, causing changes to both
structure and function. Nitrogen is an important plant nutrient, often limiting
growth in terrestrial ecosystems. Therefore, nitrogen additions can cause
increased growth which promotes the proliferation of species with a high
nitrogen demand at the expense of those species requiring less nitrogen. As
Tamm notes, most of the threatened (rare) species in central Europe have a low
nitrogen demand and therefore are most at risk from widespread increases in
nitrogen deposition. In developing countries, nitrogen has not been as clearly
studied, but many florally diverse ecosystems could be at risk if nitrogen
deposition increases.
Although freshwater ecosystems are often phosphorus limited, coastal marine
ecosystems can be very sensitive to increasing concentrations of nitrate. This
applies also in tropical regions where coral reefs may be significantly affected. The
majority of nitrate in rivers comes from the agricultural sector, but a significant
proportion comes from atmospheric deposition in some areas, such as in the
Baltic Sea where 20% of inputs derived from the atmosphere.
3 The Regional Status of Air Pollution
Driving Forces
Many developing countries have experienced progressive degradation in air
quality over the past decades. Rapid urbanization, increased industrialization
and rising energy use, mostly derived from fossil fuel combustion, have been the
major contributors. For example, energy demand in Asia and the Pacific, which
has 30 per cent of the World’s land area supporting 60% of the World population,
is growing faster than in any other part of the World.
Since 1950, the number of people living in urban areas has risen from 750
million to more than 2500 million people. The Asian and Pacific region has
experienced the greatest absolute increase in urban population, with the urban
population almost doubling between 1975 and 1995 and the trend for the growth
ecosystem sensitivity and the critical load approach on a global scale. Ambio, 2001, 30, 20—28.
Dai Zhaohua, Liu Yunxia, Wang Xinjun and Zhao Dianwu, Changes in pH, CEC and
exchangeable acidity of some forest soils in southern China during the last 32—35 years, Water, Air,
Soil Pollut., 1998, 108, 377—390.
C. O. Tamm, Nitrogen in Terrestrial Systems. Ecological Studies, 81. Springer-Verlag, 1991.
M. Enell and J. Fejes, The nitrogen load to the Baltic Sea — present situation, acceptable future
load and suggestion source reduction, Water, Air, Soil Pollut., 1995, 85, 877—882.
UNEP, Global Environment Outlook — 2. United Nations Environmental Programme, Global
State of the Environment Report 1997, Oxford University Press, New York, 2000.
J. C. I. Kuylenstierna, W. K. Hicks and M. J. Chadwick
36
Although concentration on acidification in Asia has only recently begun, several
studies have indicated evidence for soil acidification in China that may be
associated with acidic deposition. Figure 8 shows that many ecosystems in NE
and SE Asia may be very sensitive and so the risks of acidification damage may be
rather high in areas with high deposition rates.
Eutrophication. Nitrogen deposition, either as ammonium or nitrate, can
eutrophy (nutrify to excess) terrestrial ecosystems, causing changes to both
structure and function. Nitrogen is an important plant nutrient, often limiting
growth in terrestrial ecosystems. Therefore, nitrogen additions can cause
increased growth which promotes the proliferation of species with a high
nitrogen demand at the expense of those species requiring less nitrogen. As
Tamm notes, most of the threatened (rare) species in central Europe have a low
nitrogen demand and therefore are most at risk from widespread increases in
nitrogen deposition. In developing countries, nitrogen has not been as clearly
studied, but many florally diverse ecosystems could be at risk if nitrogen
deposition increases.
Although freshwater ecosystems are often phosphorus limited, coastal marine
ecosystems can be very sensitive to increasing concentrations of nitrate. This
applies also in tropical regions where coral reefs may be significantly affected. The
majority of nitrate in rivers comes from the agricultural sector, but a significant
proportion comes from atmospheric deposition in some areas, such as in the
Baltic Sea where 20% of inputs derived from the atmosphere.
3 The Regional Status of Air Pollution
Driving Forces
Many developing countries have experienced progressive degradation in air
quality over the past decades. Rapid urbanization, increased industrialization
and rising energy use, mostly derived from fossil fuel combustion, have been the
major contributors. For example, energy demand in Asia and the Pacific, which
has 30 per cent of the World’s land area supporting 60% of the World population,
is growing faster than in any other part of the World.
Since 1950, the number of people living in urban areas has risen from 750
million to more than 2500 million people. The Asian and Pacific region has
experienced the greatest absolute increase in urban population, with the urban
population almost doubling between 1975 and 1995 and the trend for the growth
ecosystem sensitivity and the critical load approach on a global scale. Ambio, 2001, 30, 20—28.
Dai Zhaohua, Liu Yunxia, Wang Xinjun and Zhao Dianwu, Changes in pH, CEC and
exchangeable acidity of some forest soils in southern China during the last 32—35 years, Water, Air,
Soil Pollut., 1998, 108, 377—390.
C. O. Tamm, Nitrogen in Terrestrial Systems. Ecological Studies, 81. Springer-Verlag, 1991.
M. Enell and J. Fejes, The nitrogen load to the Baltic Sea — present situation, acceptable future
load and suggestion source reduction, Water, Air, Soil Pollut., 1995, 85, 877—882.
UNEP, Global Environment Outlook — 2. United Nations Environmental Programme, Global
State of the Environment Report 1997, Oxford University Press, New York, 2000.
J. C. I. Kuylenstierna, W. K. Hicks and M. J. Chadwick
36