EFFECTS OF CLIMATE CHANGE ON BIODIVERSITY CONSEVARTION
INTRODUCTION.
Biodiversity, the term given to the variety of life on Earth, provides, through its
expression as ecosystems, goods and services that sustain our lives. Human pressures on
ecosystems are causing changes and losses at rates not seen historically. People are
changing ecosystems more rapidly and more extensively than over any other period in
human history. Climate change adds yet another pressure on natural ecosystems.
According to the Millennium Ecosystem Assessment, a comprehensive assessment of the
links between ecosystem health and human well-being, climate change is likely to
become the dominant direct driver of biodiversity loss by the end of the century.
Projected changes in climate, combined with land use change and the spread of exotic or
alien species, are likely to limit the capability of some species to migrate and therefore
will accelerate species loss.
The impacts of climate change on biodiversity are of major concern to the Convention on
Biological Diversity (CBD). The Convention also recognizes that there are significant
opportunities for mitigating climate change and adapting to it, while enhancing the
conservation of biodiversity. In an effort to draw attention to the mounting threats and
opportunities, the CBD is calling on the nations of the world to celebrate the International
Day for Biological Diversity on 22 May 2007 under the theme “climate change and
biodiversity”.
This paper highlights some of the causes of climate change and its impacts on
“biodiversity, as well as the various links between biodiversity and climate change. We
also present the major climate change threats that are specific to various ecosystems, as
well as the opportunities for mitigation and adaptation.
Global climate: past, present and future
The climate of the Earth has never been stable ever since the evolution of the earth and
life form. There have been periods of cooler and warmer climatic regimes. These
prehistoric changes in climate were clearly natural in origin and occurred on a planet
inhabited by primitive societies with far smaller populations than at present. Indeed, the
regularity of the diurnal and seasonal rhythms of our planet has always been overlain by
inter-annual, multi-decadal and millennial variations in climate, over whatever timescale
climate is defined. Ecosystems and species have moved, often freely, in response to such
past changes and have evolved within this climatic history.
The causes of contemporary and future changes in climate, their rate and their potential
significance for ecosystems and for the human species, however, are all notably different
from anything that has occurred previously in history or pre-history. According to Green
et al. (2003) evidence of global warming is plentiful and includes data on satellite-
measured sea level change (2 mm rise per year from 1993–2003), lengthened growing
season (by two to three weeks in the past 15–20 years) and increased precipitation
intensities resulting in increased flood risk during winter in the northern hemisphere. The
causes are now dominated by human perturbation of the atmosphere and the rate of
warming already exceeds anything experienced in the last 10,000 years. It is set to
become more rapid than anything experienced in recorded human history and, given the
ecological imprint made by our current and growing population of six billion and more,
the significance of this prospect for the natural world and for human society is
qualitatively different from previously experienced changes in climate.
The nature of the problem
The atmosphere delivers both resources (e.g. rain, sun, wind) and hazards (e.g.
hurricanes, blizzards, droughts) to ecosystems and societies. Through autonomous and/or
planned adaptation, species and individuals, ecosystems and societies, are fashioned to a
considerable extent by these climatic constraints. Ecosystems and our human cultures and
economies are ‘tuned’ to the climate in which they evolve. Yet highly successful cultures
develop in varying climates: cold/dry climates (e.g. Finland), cold/wet climates (e.g.
Iceland), hot/dry climates (e.g. Saudi Arabia) and hot/wet climates (e.g. Hong Kong). All
societies have therefore evolved strategies to cope with some intrinsic level of climatic
variability – for example, nomadic pastoralism, flood prevention, building design,
weather forecasting, early warning systems and the weather-hedging industry are all
forms of human response to the variability of climate or the extremes of weather.
Similarly, ecosystems are resilient to some extent of climatic variability, indeed may
actually require it. Consequently, there exists some level of variation in climate or some
frequency or severity of weather extremes that can be ‘accommodated’ using existing
strategies or behaviour. Exactly what can be accommodated, however, varies greatly
within and between societies and ecosystems, so that vulnerability to weather and climate
change is strongly differentiated. For example, in developed, northern nations, it is the
elderly who die during heat waves, and in developing countries, it is often the poor and
marginal who have their homes washed away in shanty towns built on flood plains.
The central concern is not that humans are altering climate – we have modified our
environment to a marked extent throughout our history – but whether these changes in
climate can be accommodated using our existing capacity to adapt, drawing upon our
intellectual, regulatory, social or financial capital and whether ecosystem resilience is
large enough to survive these climatic perturbations given the other pressures they are
subjected to by human development. An important supplementary question is whether we
can consciously enhance this adaptive capacity, especially of the most vulnerable
ecosystems and communities, to exploit the changing resources and minimize the
changing hazards delivered to us by our (now) semi-artificial climate. Additional
questions that flow from this perspective are: to what extent can we predict future
climates to assist this process of adaptation, and to what extent do we need to reduce the
size of the changes in climate facing us to allow our adaptive potential to sustain an
acceptable dynamic equilibrium between climate, ecosystems and society? extent can we
predict future climates to assist this process of adaptation, and to what extent do we need
(and desire) to reduce the size of the changes in climate facing us to allow our adaptive
potential to sustain an acceptable dynamic equilibrium between climate, ecosystems and
society?
Facing the Challenge of Climate Change
We face certainly continuing, probably accelerating and possibly unprecedented changes
in the Earth’s climate over the coming years and decades. These changes in such a
fundamental resource for society, and in such a powerful influence on ecological,
economic and cultural development, will introduce new challenges for the way we live
with and influence climate. Some of these challenges may be broadly foreseeable, many
of them may not. Some of the risks associated with a rapidly changing climate may be
quantifiable, many of them may not. What should our response be?
As evidence is emerging that some physical and biological systems are already reacting
to this human-induced change in climate, and as we know that, at least for some regions
and for some communities and ecosystems, climate variability already imposes huge
costs, doing nothing is unlikely to be the best option. Societies need to develop and
implement appropriate strategies to reduce the risks associated with a changing climate –
to ensure that these changing climatic resources are appropriately exploited and that the
adverse impacts of changing climatic hazards are minimized.
Mitigation measures are required to reduce global greenhouse gas emissions with the
intention of eventually stabilizing atmospheric concentrations at some level at which an
acceptable dynamic equilibrium could be sustained between climate, ecosystems and
human society. What this level ought to be, however, remains poorly known and
increasingly contested. On the other hand, due to the inertia of both the climate system
and our energy structures, greenhouse gases accumulated and accumulating in the
atmosphere since the pre-industrial era will continue to affect global climate long into the
future. Together with the existing exposure of many communities and assets to extremes
of weather, adaptive measures become essential in order to enhance the coping abilities
of valued ecosystems, vulnerable communities and exposed infrastructures.
These crucial perspectives about climate change need to be integrated fundamentally into
the full range of policy measures that are demanded by our drive towards sustainable
development, an argument equally valid for the nations of the south as for the nations of
the north. We all need to come to terms with climate change.
CLIMATE CHANGE VULNERABILITY IN AFRICA
While the exact nature of the changes in temperature, precipitation, and extreme events is
not known, there is agreement about the following general trends (IPCC 2000).
1. Global mean surface temperature is projected to increase between 1.5 °C (2.7°F)
and 6 °C (10.8°F) by 2100.
2. Sea levels are projected to rise by 15 to 95 centimeters (6 to 37 inches) by 2100.
3. Climate change scenarios for Africa indicate future warming across the continent
ranging from 0.2°C (0.36°F) per decade (low scenario) to more than 0.5°C (0.9°F)
per decade (high scenario) (Hulme et al. 2001; Desanker and Magadza 2001).
This warming will be greatest over the interior of semiarid margins of the Sahara
and central southern Africa.
The Multiple Impacts of Climate Change
Biodiversity Loss: Biodiversity is an important resource for African people. Uses are
consumptive (food, fiber, fuel, shelter, medicine, wildlife trade) and non-consumptive
(ecosystem services and the economically important tourism industry). Given the heavy
dependence on natural resources in Africa, many communities are vulnerable to the
biodiversity loss that could result from climate change. The impact of climate change on
humans will also be compounded by climate change-induced alterations of agriculture,
water supply and disease.
Agriculture: Most of Africa relies on rain-fed agriculture. As a result, it is highly
vulnerable to changes in climate variability, seasonal shifts, and precipitation patterns.
Any amount of warming will result in increased water stress. Roughly 70 percent of the
population lives by farming, and 40 percent of all exports are agricultural products (WRI
1996). One-third of the income in Africa is generated by agriculture. Crop production and
livestock husbandry account for about half of household income. The poorest members of
society are those who are most dependent on agriculture for jobs and income. (Odingo
1990; FAO 1999).
Impacts on Glaciers and Water Supply: The gradual yet dramatic disappearance of
glaciers on Mount Kilimanjaro is a result of global warming (IPCC 2001). An estimated
82 percent of the icecap that crowned the mountain when it was first thoroughly surveyed
in 1912 is now gone (See Figure 2). According to recent projections, if recession
continues at the present rate, the majority of the glaciers on Mount Kilimanjaro could
vanish in the next 15 years. The snow and glaciers of Mount Kilimanjaro act as a water
tower, and several rivers are drying out in the warm season due to the loss of this frozen
reservoir. Other glaciers in Africa (Ruwenzori in Uganda and Mount Kenya) are also
under similar threat.
Disease: Climate change has critical health implications. Changes in rainfall will affect
the presence and absence of vector- and water-borne pathogens (IPCC 2001). For
example, it can be expected that small changes in temperature and precipitation will boost
the population of disease-carrying mosquitoes and result in increased malaria epidemics
(Lindsay and Martens 1998). Increased flooding could facilitate the breeding of these
malaria carriers in formerly arid areas (Warsame et al. 1995).
These problems will be exacerbated by the inability of many communities to cope with
increased disease. In many African urban settlements, population expansion has outpaced
the capacity of municipal authorities to provide civic works for sanitation and other
health delivery services. If settlement conglomerations such as those envisaged for west
Africa and the eastern seaboard of South Africa develop, vulnerable populations will
cover entire regions, not just isolated areas (Nicholls et al. 1999)
Biodiversity: Africa occupies about one-fifth of the global land surface and contains
about one-fifth of all known species of plants, mammals, and birds in the world, as well
as one-sixth of amphibians and reptiles (Siegfried 1989). Climate change has already
affected the marine animals of Africa. Coral reefs in the Indian Ocean experienced
massive bleaching in 1998, with over 50 percent mortality in some regions (Spalding
2001). Damage to coral reef systems has far reaching implications for fisheries, food
security, tourism and overall marine biodiversity.
On land, animal biodiversity in Africa is concentrated in the savannas and tropical
forests. Loss or alterations of terrestrial habitats by climate change will likely impact
these species. Few detailed studies have been done on how climate change will affect
terrestrial animals in Africa, but those that have been done demonstrate the potential
extent of its impact. For example, climate change of the magnitude predicted for the
twenty-first century could alter the range of African antelope species (Hulme 1996).
World antelope biodiversity—more than 90 percent of the 80 species—is concentrated in
Africa (Macdonald 1987).
HOW CLIMATE CHANGE AFFECTS BIODIVERSITY
Direct Impacts
Climate change is likely to have a number of impacts on biodiversity – from ecosystem to
species level. The most obvious impact is the effect that flooding, sea level rise and
temperature changes will have on ecosystem boundaries, allowing some ecosystems to
expand into new areas, while others diminish in size. As well as shifting ecosystem
boundaries, these changes will also cause changes in natural habitat – an outcome which
will have a knock-on effect on species survival. A growing body of research indicates
that, as a result, climate change may lead to a sharp increase in extinction rates. Midrange predictions from one recent study suggest that 24 per cent of species in the five
study regions will be on their way to extinction by 2050 due to climate change. The study
indicates that for many species, climate change poses a greater threat to their survival
than the destruction of their natural habitat.
Global warming is also causing shifts in the reproductive cycles and growing seasons of
certain species. For example, higher temperatures have led to an increase in the number
of eggs laid by the spruce budworm, already one of the most devastating pests in North
America’s boreal forests. The impacts of climate change on biodiversity will vary from
region to region. The most rapid changes in climate are expected in the far north and
south of the planet, and in mountainous regions. These are also the regions where species
often have no alternative habitats to which they can migrate in order to survive. Other
vulnerable ecosystems and species include small populations or those restricted to small
areas