Download Global Climate Change AND Tropical Forest Ecosystems Andes

GLOBAL CLIMATE CHANGE AND TROPICAL FOREST ECOSYSTEMS
Andes Hamuraby Rozak
Cibodas Botanic Gardens – Indonesian Institute of Sciences
Jl. Kebun Raya Cibodas, Cipanas, Cianjur, West Java 43253 Indonesia
(phone: +62-263-520448; fax: +62-263-512233)
e-mail: [email protected]
Key words: Climate change, biodiversity, tropical forest ecosystems
Article type Scientific Review
Word count abstract 105
Word count main text 1310
Number of references 18
Number of tables Number of figures 2
ABSTRACT
In the last 100 years, the global mean temperature has increased approximately 0.6 oC and predicted will increase
approximately 1.1oC to 6.4oC in the last 21st century. This global climate change phenomenon in physical
dimension has been analyzed in detail but still poorly understood its effect to the changes of biodiversity
particularly in tropics. In this paper, I discussed brief review about climate change, current status of forest
ecosystems, and the effect of global climate change particularly for tropical forest ecosystems. Furthermore, in
the last part, I discussed brief review about the reverse effect which is the effect of the deforestation to the
regional climate change.
Keywords: Climate change, biodiversity, tropical forest ecosystems
INTRODUCTION
Global climate change is now a well-known complex phenomenon and is often discussed
with a view to mitigating the effects of anthropogenic emissions of greenhouse gases.
Although the physical dimensions have been analyzed in detail, the effect of global climate
change on biodiversity, particularly in the tropics, are poorly understood (Meynecke, 2004).
The evidence for biotic responses to global climate change is clear for high latitudes but
sparse and controversial for tropical latitudes (Wright, 2005). For instance, the study of
Pompe et al. (2008) showed that climate change impacts on plant distribution in Germany.
The effect of climatic change on tropical vegetation becomes global and regional concern
because of the high biodiversity and the potential feedback to the carbon, water, and nutrient
cycles (Ostendorf et al., 2001). Tropical forests is one of the tropical vegetation that already
facing threats from deforestation, fragmentation and habitat degradation (Giam et al., 2010).
They are likely to encounter further challenges from the ongoing and impending changes in
climate. Although the role of tropical forests as both sinks and sources of CO2 has been well
recognized, less is known about the impact of climate change on tropical biotas (Bawa &
Markham, 1995).
Tropical forests are among the biologically richest ecosystems on Earth, but are being rapidly
degraded and destroyed by habitat conversion (Myers et al., 2000). These forests are also
vulnerable to global warming and other large-scale environmental change, but much
uncertainty exists about the nature and magnitude of these anthropogenic impacts in tropical
forest organisms (Laurance et al., 2011).
CURRENT STATUS OF FOREST ECOSYSTEMS
FAO (2006) and IPCC (2007a) reported that the global forest cover is 3,952 million hectares,
which is about 30 percent of the world’s land area (Figure 1a). Most relevant for the carbon
cycle is that between 2000 and 2005, gross deforestation continued at a rate of 12.9 million
hectares/year (Figure 1b). This is mainly as a result of converting forests to agricultural land,
but also due to expansion of settlements, infrastructure, and unsustainable logging practices.
In the 1990s, gross deforestation was slightly higher, at 13.1 million hectares/year. Due to
afforestation, landscape restoration and natural expansion of forests, the most recent estimate
of net loss of forest is 7.3 million hectares/year. The loss is still largest in South America,
Africa and Southeast Asia. This net loss was less than that of 8.9 million hectares/year in the
1990s.
GLOBAL CLIMATE CHANGE
Climate change refers to a change in the state of the climate that can be identified by changes
in the mean and/or the variability of its properties and that persists for an extended period,
typically decades or longer (IPCC, 2007b). Over the past 100 year, the global average
temperature has increased by approximately 0.6oC and is projected to continue to rise at a
rapid rate (Root et al., 2003). IPCC (2007b) was reported the projection of the average
surface temperature in six different scenarios (B1, B2, A1B, A1T, A2, and A1FI). The
lowest future emissions trajectory scenario (B1) predicted that the surface temperature will
increase 1.8oC (1.1oC to 2.9oC) in 2100, meanwhile, the highest future emissions trajectory
scenario (A1FI) predicted that the surface temperature will increase 4.0oC (2.4oC to 6.4oC) in
2100 (Figure 2). It means that by the end of the 21st century, large portions of the Earth’s
surface may experience climates not found at present and some 20th century climates may
disappear (Root et al., 2003).
CLIMATE CHANGE EFFECTS TO FOREST ECOSYSTEMS
Climate is one of the primary constraints on species distributions and ecosystem function and
Ecologists are faced with the challenge of forecasting species range shifts, extinction risks,
biome shifts, altered disturbance regimes, biogeochemical cycling, and other ecological
responses to climate change (Williams et al., 2007). Simulation study in order to investigate
the response of vegetation to global warming and rainfall anomalies has been done by White
et al. (1999). White et al. found that there are four key changes predicted that will change in
vegetation area. Those four key changes are:
1. Some areas of tropical evergreen forest in Amazonia were predicted to change to
savanna, grassland or even desert by the 2080s, in response to warming of over 7 oC
and decreases in rainfall of up to 500mm y-1,
2. Large areas of tropical C4 grassland (e.g. in the Sahel, India and Australia) were lost
to desert by the 2080s in response to warming, increasing CO2 and decreased rainfall,
or superseded by C3 grassland where rainfall increased,
3. Annual precipitation decreases of up to 200mm y-1 resulted in the conversion of large
area of temperate forest to grassland or savanna in southern Europe and eastern
United States,
4. Needle-leaved boreal forest extended northwards response to warming, with loss of
tundra and southwards in Asia in response to increased precipitation.
Another study in tropical forest located in Northern Queensland Australia has been done by
Ostendorf et al. (2001). Ostendorf et al. evaluate how the spatial arrangement of forest
pattern may constrain vegetation change as predicted by spatially static artificial neural
network (ANN) model. The ANN model quantifies a most suitable forest type based on the
conditional on the transition to the best-suited type. In that model, they evaluates the effect
of the increase 10C mean annual temperature and the decrease 10% mean annual
precipitation change. Depending on the strength of spatial effects included in the models, the
predicted future vegetation pattern differ 1% to 10% of the study area. However, if in
addition to spatial constraints ecological constraints also considered, the predictions may
differ by as much as 27% showing a relatively strong dependence of prediction on
assumptions about patch-level processes.
Tropical montane forest ecosystems are also affected by climate change. Foster study (2001)
tried to explain the negative potential impacts of climate change on tropical montane cloud
forests. He argued that the cloud forest will also be affected by climate changes, in particular
changes in cloud formation. A number of global climate models suggest a reduction in low
level cloudiness with the coming climate changes. One site in particular, Monteverde - Costa
Rica, appears to already be experiencing a reduction in cloud immersion. The coming
climate changes appear very likely to upset the current equilibrium of the cloud forest.
Results will include biodiversity loss, altitude shifts in species’ ranges and subsequent
community reshuffling, and possibly forest death. He also mentioned that the difficulties for
cloud forest species to survive in climate-induced migrations include no remaining location
with suitable climate, no pristine location to colonize, migration rates or establishment rates
that cannot keep up with climate change rates and new species interactions.
FOREST ECOSYSTEMS EFFECTS TO REGIONAL CLIMATE CHANGES
In other perspectives, million hectares of forest has been changed into unforested area caused
by forest fire, illegal logging, land use changes (Flannigan et al., 2000) The deforestation of
the areas is affecting the regional climates especially for the increasing of green house gasses
(van der Werf et al., 2008).
McGuffie et al. (1995) describes the impacts of tropical
deforestation on regional climates in terms of change detected in five regions i.e. Northern
Amazon, Southern Amazon, Central Amazon, Southeast Asia, and Africa. For each of these
regions, seasonal distributions of three climatic variables are discussed which are the ground
(or soil) surface temperature, the total precipitation and the atmospheric moisture
convergence. The McGuffie’s results showed that precipitation always decreases following
tropical deforestation.
Although the ground surface temperature increases in southern
Amazon and over Basin as a whole, the northern Amazon, Southeast Asia and Africa all
exhibit decreases in ground temperatures.
Then, atmospheric moisture convergence
decreases in the Amazon. In contrast, the moisture convergence is increased over Southeast
Asia and similar effect can be seen in Africa. These changes suggest that regional-scale
circulation have been affected by tropical deforestation. If this is the case, then it is possible
that locations distant from the disturbed tropics may also be affected.
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Figures
Figure 1. (a) World’s forest area; (b) Net change in forest area between 2000 and 2005 (FAO, 2006)
Figure 2. IPCC multi-model averages and assessed ranges for surface warming in six different
emissions scenarios.