Geography Reference
In-Depth Information
troposphere and global warming may interact
with acid precipitation to cause ecosystem
damage.
The deposition of nitrous and sulphurous
acids increases the hydrogen ion content of the
soil and causes declines in essential plant
nutrients (see Part II); as microbial activity
decreases, fungi dominate the decomposer
system. Populations of earthworms and other soil
fauna are reduced, which limits soil mixing,
drainage and aeration. The loss of bases and other
essential nutrients also impairs vegetation growth.
This is illustrated by Likens
et al
. (1996), who
have monitored soil and water chemistry in the
Hubbard Brook Experimental Forest ecosystem,
New Hampshire, USA, over many years. There
have been substantial declines in total soil
calcium and magnesium; this may impair
ecosystem recovery as acid emissions decrease. A
decline in soil calcium and magnesium is also
considered to be a major cause of forest decline
in the Kola Peninsula of Russia, where the major
emitter of acid precipitation is a nickel smelter
(Koptsik and Mukhina 1995). All of these factors
and possibly others may be responsible for what
is recognised as a substantial decline in forest
health in Europe and elsewhere. The case of
European forest damage is discussed in Box 3.2
and a detailed study of forest cover change in the
Czech Republic is detailed in Ardö
et al
. (1997).
Most peatlands are naturally acid and thus
offer little buffering capacity to acid
precipitation. Moreover, where they are in the
immediate hinterland of heavily industrialised
areas, ecological damage can be considerable. This
is exemplified by blanket peats in the Pennines
of the UK. According to Lee's (1998) review, the
area of peatland between Manchester and
Sheffield received considerable quantities of
sulphur dioxide from these major industrial
centres during the 1800s and early 1900s (prior
to control measures on particulate emissions in
the 1950s). The impact of this contamination
involved a loss of biodiversity, notably of
Sphagnum
species; these bog-forming mosses are
particularly susceptible to pollutants because they
rely heavily on atmospheric deposition for their
Box 3.2
Forest damage in Europe
1 Acid precipitation is a major contributory cause of
forest damage in Europe.
2 Other factors include drought, although drought
occurrence may have a greater impact in acid-
damaged areas, e.g. southern Poland, than in areas
where there is little such damage.
3 The impact of acid precipitation on forest soils is
likely to influence the degree of forest damage.
Cations, essential nutrients such as magnesium and
calcium, may be removed from the ecosystem, while
heavy metals, which are also deposited in acid
precipitation, may have a toxic effect.
4 Not only is the forest canopy damaged but ground
flora may also be altered, with a shift towards
acidophilous species such as heather.
5 The distribution of forest damage in Europe is given
in the map below. This shows that the greatest
damage has occurred in Eastern and Central
Europe, with least damage in western maritime
regions.
Source:
Based on Elvingson 1997.
nutrient supply. Where species are lost and
peatlands become increasingly acidic, erosion
may set in as the surfaces lose their protective
vegetation cover.
The impact of acid precipitation on urban fabrics,
urban air quality and archaeological monuments
Acid emissions do not discriminate between rural
and urban environments. Indeed, emissions in
