formation (Archibold, 1995). Nitrogen enters bogs mainly
through wet and dry atmospheric deposition and is particularly low in wetland ecosystems (Morris, 1991). Vegetation in bogs has adapted to these nutrient-deficient
habitats. For example, vascular plants and bog shrubs in
bogs withdraw nitrogen and other species (e.g., P, K) out
of organs and foliage before it is shed (Archibold, 1995).
Microbial activity is also poor in bogs due to the poor substrate induced from low nutrient levels, which reduces
microorganisms in acid peat. Organisms that feed upon
fungi and bacteria are therefore also restricted.
Geographic distribution
Although a global wetland inventory still remains incomplete, total wetland area is currently accepted to be
between 8 and 10 million km
2 or 6–8 % of the land surface of the earth (Lehner and Döll, 2004). Wetland distribution is roughly bimodal with approximately 50 %
located in boreal and arctic regions (e.g., 50 to 70ºN,
dominated by boreal peatlands) and about 35 % located
in tropical/subtropical regions (between 20ºN and 30ºS,
dominated by swamps and marshes) (Matthews, 2000).
In terms of peatlands, total area is estimated at about
3 % of the earth’s land surface (or about 4 million km
2 )
(Gorham, 1991). Peat formation is primarily dictated by
climate, and therefore peatland distribution is mainly
concentrated across specific climate regions. Therefore,
peatlands are particularly abundant in cold (boreal and
subarctic) and wet (tropical/subtropical and oceanic)
regions as described earlier. This geographic distribution
can be explained by two main reasons: (1) water is the
most important factor controlling peat accumulation
and (2) temperature directly affects the production and
decay of organic matter (Parish et al., 2008). The presence of large peatlands such as western Siberia, the Hudson Bay Lowlands, or the Amazon Basin is also
a consequence of large flat surfaces that allow water logging conditions. North American peatlands represent
about 45 % of global peatland area, followed by
peatlands in Asia (about 37 %), Europe (12 %), South
America (4 %), Africa (1.4 %), Oceania (0.1 %), and
Antarctica (0 %) (Parish et al., 2008).
Uses
Peatlands (and wetlands in general) are one of the most
important natural ecosystems in the world and recognized
to perform many ecological functions. Wetlands are
among the most productive ecosystems, comparable to
rain forests and coral reefs. The US Fish and Wildlife
Service estimates that 43 % of endangered species relies
on wetlands for survival. Peatlands provide numerous
benefits, such as unique wildlife habitats, biodiversity
conservation and climate regulation, natural mechanisms
for water purification, flood storage, recreational opportunities, and natural products for societal use. They are
important in the biogeochemical cycling of nutrients,
providing the necessary conditions for nutrient removal
from surface waters. Peatlands account for about 33 %
of terrestrially stored soil carbon, and they are hence
directly related to the global carbon cycle and impact
greenhouse gas concentrations, such as methane (CH 4 )
and carbon dioxide (CO 2 ) in the atmosphere (Gorham,
1991). For example, emissions from northern peatlands
have been estimated to account for approximately 7 % of
the global annual emission of methane to the atmosphere
(Khalil, 2000).
Common peatland uses include (Parish et al., 2008)
(1) agriculture, such as grazing and growing crops, often
resulting in drainage and subsequent problems of subsidence, fire, and soil deterioration; (2) forestry such as timber harvesting; (3) peat extraction, commonly for fuel;
(4) water regulation, acting as water reservoirs for drinking water; (5) biodiversity, including specialized organisms that are adapted to the unique conditions;
(6) research, education, and recreation acting as archives
and often important for tourism; and (7) carbon storage,
containing nearly 30 % of all carbon on the land.
Environmental importance and climate change
Peatlands are important global stores of carbon and
a critical component of climate regulation; however, their
response to global warming is still a major uncertainty in
climate modeling (Wania et al., 2004). Peatlands have
absorbed about 1.2 trillion tones of carbon dioxide over
the past 10,000 years inducing a net cooling effect on
the earth. Recent studies, however, indicate that degradation and drainage of peatlands has converted many
peatlands from a net store to a source of carbon emissions
(Parish et al., 2008). Although the fate of peatlands when
subject to changes in global temperature and rainfall
regime is still uncertain, most predictions agree that
changes will have a negative impact on peatlands by
accelerating rate of degradation and release of stored carbon (IPCC, 2007). Such degradation will likely result in
an increase in greenhouse gas emissions affecting millions of people around the world the way it is already
occurring in Southeast Asian peat swamp forests after
drainage and fires or from the threatening effects on the
water and food supply after the destruction of peatlands
in Africa, Asia, or Latin America.
Although present coverage represents less than 3 % of
the earth’s land surface, C storage in peatlands is estimated
between 270 and 370 Tg C, approximately amounting for
35–50 % of the total 796 Tg C held in the atmosphere as
CO 2 (IPCC, 2007). Tropical peatlands show the highest
uncertainties from all estimates, with C stores ranging
between 8 and 258 Tg C (Hooijer et al., 2006). Peatlands
are also important sources of atmospheric methane, but
methane-producing bacteria in the deeper parts of the
bog are postulated to generate a reservoir of free-phase
methane (Romanowicz et al., 1995). Recent work
suggests that the mass of free-phase gas in peatlands is
478
PEAT
through wet and dry atmospheric deposition and is particularly low in wetland ecosystems (Morris, 1991). Vegetation in bogs has adapted to these nutrient-deficient
habitats. For example, vascular plants and bog shrubs in
bogs withdraw nitrogen and other species (e.g., P, K) out
of organs and foliage before it is shed (Archibold, 1995).
Microbial activity is also poor in bogs due to the poor substrate induced from low nutrient levels, which reduces
microorganisms in acid peat. Organisms that feed upon
fungi and bacteria are therefore also restricted.
Geographic distribution
Although a global wetland inventory still remains incomplete, total wetland area is currently accepted to be
between 8 and 10 million km
2 or 6–8 % of the land surface of the earth (Lehner and Döll, 2004). Wetland distribution is roughly bimodal with approximately 50 %
located in boreal and arctic regions (e.g., 50 to 70ºN,
dominated by boreal peatlands) and about 35 % located
in tropical/subtropical regions (between 20ºN and 30ºS,
dominated by swamps and marshes) (Matthews, 2000).
In terms of peatlands, total area is estimated at about
3 % of the earth’s land surface (or about 4 million km
2 )
(Gorham, 1991). Peat formation is primarily dictated by
climate, and therefore peatland distribution is mainly
concentrated across specific climate regions. Therefore,
peatlands are particularly abundant in cold (boreal and
subarctic) and wet (tropical/subtropical and oceanic)
regions as described earlier. This geographic distribution
can be explained by two main reasons: (1) water is the
most important factor controlling peat accumulation
and (2) temperature directly affects the production and
decay of organic matter (Parish et al., 2008). The presence of large peatlands such as western Siberia, the Hudson Bay Lowlands, or the Amazon Basin is also
a consequence of large flat surfaces that allow water logging conditions. North American peatlands represent
about 45 % of global peatland area, followed by
peatlands in Asia (about 37 %), Europe (12 %), South
America (4 %), Africa (1.4 %), Oceania (0.1 %), and
Antarctica (0 %) (Parish et al., 2008).
Uses
Peatlands (and wetlands in general) are one of the most
important natural ecosystems in the world and recognized
to perform many ecological functions. Wetlands are
among the most productive ecosystems, comparable to
rain forests and coral reefs. The US Fish and Wildlife
Service estimates that 43 % of endangered species relies
on wetlands for survival. Peatlands provide numerous
benefits, such as unique wildlife habitats, biodiversity
conservation and climate regulation, natural mechanisms
for water purification, flood storage, recreational opportunities, and natural products for societal use. They are
important in the biogeochemical cycling of nutrients,
providing the necessary conditions for nutrient removal
from surface waters. Peatlands account for about 33 %
of terrestrially stored soil carbon, and they are hence
directly related to the global carbon cycle and impact
greenhouse gas concentrations, such as methane (CH 4 )
and carbon dioxide (CO 2 ) in the atmosphere (Gorham,
1991). For example, emissions from northern peatlands
have been estimated to account for approximately 7 % of
the global annual emission of methane to the atmosphere
(Khalil, 2000).
Common peatland uses include (Parish et al., 2008)
(1) agriculture, such as grazing and growing crops, often
resulting in drainage and subsequent problems of subsidence, fire, and soil deterioration; (2) forestry such as timber harvesting; (3) peat extraction, commonly for fuel;
(4) water regulation, acting as water reservoirs for drinking water; (5) biodiversity, including specialized organisms that are adapted to the unique conditions;
(6) research, education, and recreation acting as archives
and often important for tourism; and (7) carbon storage,
containing nearly 30 % of all carbon on the land.
Environmental importance and climate change
Peatlands are important global stores of carbon and
a critical component of climate regulation; however, their
response to global warming is still a major uncertainty in
climate modeling (Wania et al., 2004). Peatlands have
absorbed about 1.2 trillion tones of carbon dioxide over
the past 10,000 years inducing a net cooling effect on
the earth. Recent studies, however, indicate that degradation and drainage of peatlands has converted many
peatlands from a net store to a source of carbon emissions
(Parish et al., 2008). Although the fate of peatlands when
subject to changes in global temperature and rainfall
regime is still uncertain, most predictions agree that
changes will have a negative impact on peatlands by
accelerating rate of degradation and release of stored carbon (IPCC, 2007). Such degradation will likely result in
an increase in greenhouse gas emissions affecting millions of people around the world the way it is already
occurring in Southeast Asian peat swamp forests after
drainage and fires or from the threatening effects on the
water and food supply after the destruction of peatlands
in Africa, Asia, or Latin America.
Although present coverage represents less than 3 % of
the earth’s land surface, C storage in peatlands is estimated
between 270 and 370 Tg C, approximately amounting for
35–50 % of the total 796 Tg C held in the atmosphere as
CO 2 (IPCC, 2007). Tropical peatlands show the highest
uncertainties from all estimates, with C stores ranging
between 8 and 258 Tg C (Hooijer et al., 2006). Peatlands
are also important sources of atmospheric methane, but
methane-producing bacteria in the deeper parts of the
bog are postulated to generate a reservoir of free-phase
methane (Romanowicz et al., 1995). Recent work
suggests that the mass of free-phase gas in peatlands is
478
PEAT