TERRESTRIAL BIODIVERSITY
Biodiversity
is the web of life that distinguishes planet Earth from the other lifeless
spheres in our solar system, if not the universe. There are three different
levels of diversity: ecosystem diversity, species diversity, and genetic
diversity (i.e., diversity within species). We focus here on terrestrial (as
opposed to aquatic) ecosystem diversity, and on species diversity within
terrestrial ecosystems.
The number
and types of organisms inhabiting the planet have varied immensely during
geologic history. In part, these variations have been caused by the evolution
of new types of organisms and the elimination of others due to environmental
changes and mass extinctions, as occurred at the end of the Mesozoic period 65
million years ago which saw the extinction of the dinosaurs.
Now,
however, human transformations of the earth's surface are a force of geologic
proportions that is affecting biodiversity in almost every corner of the world.
Changes are occurring rapidly enough that the result is a net loss of species
rather than a proliferation of new life forms. Species have been disappearing
at 50-100 times the natural rate, and this is predicted to rise dramatically.
Based on current trends, an estimated 34,000 plant and 5,200 animal species -
including one in eight of the world's bird species - are critically endangered.
The
greatest human impact on biodiversity is the alteration and destruction of
habitats, which occurs mainly through changes in land use: draining of
wetlands, clearing of land for agriculture, felling of forests for timber, and
pollution of the environment and fragmentation. Other impacts on biodiversity
include the development and potential proliferation of genetically modified
organisms (GMOs), direct exploitation (e.g., over-harvesting of plants or
animals), and introduction of alien (non-native) species.
Loss of
species is significant in several respects. First, breaking of critical links
in the biological chain can disrupt the functioning of an entire ecosystem and
its biogeochemical cycles. This disruption may have significant effects on
larger scale processes. Second, loss of species can have impacts on the
organism pool from which medicines and pharmaceuticals can be derived.
Third,
loss of species can result in loss of genetic material, which is needed to
replenish the genetic diversity of domesticated plants that are the basis of
world agriculture (Convention on Biological Diversity).
In recent
years, the international scientific community has made considerable progress
toward fostering global awareness of the importance of biodiversity. As a
result, a number of multiagency organizations have been established, and many
conservation programs have been implemented.
BIODIVERSITY HOTSPOTS
A variety of approaches have
been utilized to identify areas of high species richness and endemism. A biodiversity hotspot is a biogeographic
region with a significant reservior of biodiversity that is threatened with
destruction.
The concept of biodiversity hoptspots was originated by Dr. Norman Myers in
two articles in the scientific journal ‘The Environmentalist’ (1988 &1990)
revised after thorough analysis by myers and others in ‘Hotspots: Earth’s
Biological Richest and Most Endangered Terrestrial Ecoregions’ (1999). The
hotspots ideas was also promoted by Russell Mittermeier in the popular book
‘hotspots revisited’ (2004), although this has not been subjected to scientific
peer-review like the other hotspots analysis.
The term "hotspots"
indicate areas of high conservation value that are facing significant threats
to conservation. Myer's first version was entirely focused on tropical rain forests.
In its most recent iteration, the hotspots analysis identified 25 high priority
areas, including some temperate areas such as the California coast, the
Mediterranean and New Zealand.
To qualify as a biodiversity hotspots, a region must two strict criteria :
it must contain at least 1,500 species of vascular plants as endemics, and it
has to have lost at least 70 % of its original habitat. Around the world, at
least 25 areas qualify under this definition, with nine other possible
candidtes. These sites support nearly 60 % of the world’s plant, bird, mammal,
reptile, and amphibian species, with a very high share of endemic species.
Dense human habitation tends to occur near hotspots. Most hotspots are
located in the tropics and most of them are forests.
The
biodiversity hotspots by region
North and Central America
1.
California
Floristic Province
2.
Caribbean
Islands
3.
Madrean
Pine Oak Woodlands
4.
Mesoamerica
South America
1.
Atlantic
Forest
2.
Cerrado
3.
Chilean
Winter Rainfall-Valdivian Forests
4.
Tumes-Choco-Magdalena
5.
Tropical
Andes
Europe and Central Asia
1.
Caucasus
2.
Irano-Anatolian
3.
Mediterranean
Basin
4.
mountains
of Central Asia
Africa
1.
Cape
Floristic Region
2.
Coastal
Forests of Eastern Africa
3.
Eastern
Afromntane
4.
Guinean
Forests of Eastern Africa
5.
Horn
of Africa
6.
Coastal
Forests of Eastern Africa
7.
Madagascar
and the Indian Ocean Islands
8.
Maputaland
Pondoland Albany
9.
Succulent
Karoo
Asia – Pacific
1.
East
Melanesian Island
2.
Eastern
Himalaya
3.
Indo-Burma
4.
Japan
5.
Mountains
of Southwest China
6.
New
Caledonia
7.
New
Zealand
8.
Philippines
9.
polynesia-Micronesia
10.
Southwest
Australia
11.
Sundaland
12.
Wallacea
13.
Western
Ghats and Sri Lanka
Brazil's Atlantic Forest is considered a hotspot of biodiversity and
contains roughly 20,000 plant species, 1350 vertebrates, and millions of
insects, about half of which occur nowhere else in the world. The island of
Madagascar including the unique Madagascar dry deciduous forests and lowland
rainforests possess a very high ratio of species endemism and biodiversity,
since the island separated from mainland Africa 65 million years ago, most of
the species and ecosystems have evolved independently producing unique species
different from those in other parts of Africa.
Many regions of high biodiversity (as well as high endemism) arise from
very specialized habitats which require unusual adaptation mechanisms. For
example the peat bogs of Northern Europe and the alvar regions such as the
Stora Alvaret on Oland, Sweden host a large diversity of plants and animals,
many of which are not found elsewhere.
The Global
200 approach, adopted by the World Wide Fund for Nature (WWF), identifies 233
high priority areas that are globally representative of all habitat types.
Olson and Dinerstein in 1998 suggest that although tropical moist forests
contain over half of all species diversity, the many other ecosystems that
contain the remaining 50 percent also deserve consideration. These include
tropical dry forests, tundra, temperate grasslands, polar seas, and mangroves,
which all contain unique expressions of biodiversity with characteristic
species, biological communities, and distinctive ecological and evolutionary
phenomena. Given their focus on ecoregions, large units of land or water
containing a characteristic set of natural communities, and given the large
number of regions included on the list, the Global 200 ecosystems comprises a
much larger proportion of the terrestrial land surface.
Hotspots
and the Global 200 represent priority-setting efforts that focuses on high
value and highly threatened ecosystems. The Global 200 report states that, among
terrestrial ecosystems included on their list, 47 percent are considered
critical or endangered and 29 percent are vulnerable, leaving a little over a
quarter that are stable or intact. An alternative approach, developed by
Wildlife Conservation Society and CIESIN (2002), is to identify the world's
last great wild areas, and to concentrate resources and attention to securing
as much of those regions under some kind of conservation status. Presumably,
this can be done at far less cost than conservation in densely settled areas.
Ultimately, however, the two approaches are complimentary. The hotspots
approach is undertaken in combination with efforts to conserve the last
remaining "pristine" wilderness areas.
Approaches to Biodiversity Conservation
There are
some major approaches to conservation policy :
Traditional Protected Areas
Traditional
protected areas harness the power of the state to define areas in which varying
degrees of conservation (from strict preservation to protected multi-use
landscapes), to set policies for land and resource use, and to enforce those
policies through allocation of resources and prosecution of offenders.
Collaborative Management
Collaborative
management or community-based natural resource management works with multiple
stakeholders - government, community, and private sector - to identify and
implement approaches to conservation that may include varying degrees of
sustainable natural resource use. These two approaches are not mutually
exclusive, and many instances of collaborative management in and around
protected areas have been documented.
Conservation Corridor
There are
also a number different approaches or theories that guide on-the-ground
conservation as it relates to land use and land cover. One of these is the development
of conservation corridors that connect a series of protected areas with
protected landscapes so as to provide animal migration routes in response to
habitat fragmentation. In Central America, which owing to its location as a
land bridge between North and South America contains some 7-8 percent of the
world's biodiversity on just one percent of its land surface, an ambitious
initiative is underway to create a Mesoamerican
Biological Corridor (MBC). The
MBC intends to use a combination of land purchases and incentives to convince
farmers living in the corridors to abandon slash and burn agriculture and
cattle ranching for planting shaded coffee and cacao, which an serve as habitat
for birds. Similar corridor initiatives have been undertaken to link habitat
remnants in Florida, and new initiatives are planned for Europe, western
Australia, the Himalayas, and Brazil's Amazon and Atlantic forests.
Gap Analysis
Gap
analysis is a tool that was developed to identify the gaps between
species distribution and existing protected areas. In contrast to a
species-by-species approach, or habitat protection for a single flagship
species (e.g., lions or pandas), gap analysis identifies the gaps in
representation of biodiversity in areas managed exclusively or primarily for
the long term maintenance of populations of native species and natural
ecosystems. Once identified, gaps are filled through new reserve acquisitions
or designations, corridors, or through changes in management practices.
Conservation of Agro-Biodiversity through Improved
Land-Management
This is an
important objective of the Convention on Biological Diversity. A dozen crops
together provide about 75 percent of the world's caloric intake. In terms of
animal protein intake, just three domestic animals - pigs, cattle and chickens
- constitute the largest sources.
The importance of this greatly reduced number
of crops and animals means that conscious efforts will need to be taken to
protect agro-biodiversity, if not for other reason because little utilized or
exploited crop varieties provide important genetic information that can help to
combat diseases and pests in the future. Some of the most valuable genetic
resources are in the fields of subsistence farmers in the developing world, and
countries like Mexico have made a conscious effort to exclude genetically
modified crops in order to preserve the purity of their local varieties.
BIODIVERSITY AND CLIMATE CHANGE
There are a
number of major issues at the interface of biodiversity, land use and climate change.
As climate changes, ecosystems will respond to changes in temperature and
precipitation as well as changes in the carbon-dioxide concentrations in the
atmosphere.
These changes are likely to favor some species and to negatively
affect others, which will alter competitive relationships and may cause
invasions by "generalist" species (Walker and Steffan 1997). Perhaps
most significantly, there is a risk that climatic changes will occur more
rapidly than individual species are able to adapt.
For those species that are
able to migrate with climate change (seeking appropriate habitat as it
literally moves out from under them), there is a risk that migration
"escape routes" will be closed due to anthropogenically altered
landscapes or natural barriers, such as mountains, rivers and oceans (Malcolm
and Markham 2000).
The ultimate result could be large-scale extinctions.
An analysis
of WWF's Global 200 ecosystems suggests that more than 80 percent of these
biologically rich regions will suffer extinctions of plant and animal species
as a result of global warming; changes in habitats from global warming will be
more severe at high latitudes and altitudes than in lowland tropical areas; the
most unique and diverse natural ecosystems may lose more than 70 percent of the
habitats upon which their plant and animal species depend; and many habitats
will change at a rate approximately ten times faster than the rapid changes
during the recent postglacial period (Malcolm et al. 2002).
Unlike the introduction of
invasive species, land conversion, and other threats to biodiversity, because
climate is globally pervasive, it will affect even remote wilderness areas that
to date have experienced little of anthropogenic change. Walker and Steffan
predict that more natural ecosystems will be in an early successional state,
and that the biosphere will be "weedier" and structurally simpler, by
comparison with ecologically complex old-growth areas.
The study of climate
change impacts on biodiversity is still in its infancy, but several path
breaking workshops and research initiatives suggest future research directions
for those interested in how humanity can mitigate the impacts of climate change
on other species (Global Change in Terrestrial Ecosystems, IAI 1994). There is
also increasing interest in how to address, at the policy level, the complex
linkages between climate change and biodiversity (IUCN 2001, Convention on
Biological Diversity).
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