Transcript THREATS TO GLOBAL BIODIVERSITY

THREATS TO GLOBAL
BIODIVERSITY
The worst thing that can happen during the 1980s is not
energy depletion, economic collapse, limited nuclear
war, or conquest by a totalitarian government. As
terrible as these catastrophes would be for us, they can
be repaired within a few generations. The one process
ongoing in the 1980s that will take millions of years to
correct is the loss of genetic and species diversity by the
destruction of natural habitats. This is the folly that our
descendents are least likely to forgive us.
E.O. Wilson, 1985
THREATS TO GLOBAL
BIODIVERSITY
We wish to know:
What is biodiversity?
What are the threats to biodiversity?
How can we estimate rates of
species loss?
What is Biodiversity?
the variety and variability among living
organisms and the ecological complexes in
which they occur
number and variety of species, ecological
systems, and the genetic variability they
contain.
In its narrowest sense biodiversity refers
to the number of species on the planet
How Many Species Exist?
1.4 million species are "known to science"
-- meaning that they have been classified
by a specialist
Most experts estimate the world's species
diversity at 10 to 30 million, but that is
very approximate
Except for land vertebrates and flowering
plants, the number of undescribed species
(greatly) exceeds the number described
Number of Known, Living, Species
Among species
known to science,
the insects are
overwhelming in
number. For this
reason, most animal
species live on land,
but more phyla, the
highest level of
classification, live in
the sea.
Number of Animal Species
Currently Known
Number of Living Species of Higher
Plants
Plant diversity of the
world consists primarily
of the flowering plants
(angiosperms), which is
divided into the grasses
and other monocots,
and a great variety of
dicots. Most flowering
plants live on land;
algae prevail in the sea.
The Geography of Biodiversity
The number of species is greatest near the
equator, and declines as one moves towards the
poles.
Tropical rain forests are especially rich
Certain areas harbor an unusually rich local
diversity, perhaps because conditions favor
evolutionary diversification.
Certain areas (islands in particular) contain
species unique (“endemic”) to that locale
Global Biodiversity
GLOBAL BIODIVERSITY map of the distribution of some of the most highly valued
terrestrial biodiversity world-wide (mammals, reptiles, amphibians and seed plants), using
family-level (red for high biodiversity and blue for low biodiversity).
http://www.nhm.ac.uk/science/projects/worldmap/
Threats to Biodiversity
Human actions now threaten species and
ecosystems to an extent rarely seen in earth
history.
Over-harvesting
habitat destruction (degradation,
fragmentation)
exotic species
domino effects
pollution
climate change
Over-Exploitation
Hunting, especially
commercial hunting and
poaching, has driven
many species to
extinction.
Passenger pigeon for
meat, snowy egret for
fashion, rhinos for their
horns.
Bushmeat harvest is a
crisis of tropical forests
today
Invading Species
Non-indigenous
species (invaders)
often are more
effective predators or
competitors, thereby
eliminating native
species. Island (and
lake) species may be
especially vulnerable.
Nutria (Coypu)
Nutria begging for duck food at a
park in Louisiana
http://www.keigh.com/nutria.html
The nutria is a 7-kg rodent
native to South America,
introduced into many areas
of the USA and UK for fur.
They devour crops and native
plants, burrow into dikes and
levees.
A six-year campaign in Britain
exterminated the nutria in
1989
Maryland DNR hopes to
accomplish their eradication
from the Blackwater National
Wildlife Refuge on
Maryland’s eastern shore.
A Michigan Invader
The gypsy moth arrived
in the U.S. in the early
1900s, and in Michigan
in the 1950s. With few
natural enemies, it
devours the leaves of
forest trees. Although
some defoliation is
tolerable, if in two
successive years and
coupled with a drought,
trees can be killed.
Global Deforestation
Original tropical
forest extent was
~ 15 m km2;
today it is about
8 m km2. At
present rates of
loss, ~ 10% of
the original
tropical forests
will remain by
end of century.
As climate
warms in
northern
Minnesota,
conifer and
broadleaf forests
will be replaced
by savannah and
woodland.
Under a 2 x CO2
scenario, the
bobolink’s habitat
would shift northwards
Forests at Risk from Global
Warming -- WWF
Studies of plant and
animal biogeography
have established a loglinear relationship
between number of
species in an area, and
areal extent. An example
for the reptiles and
amphibians for the
Caribbean is shown with
the area axis reversed, to
illustrate that reduction in
area leads to a reduction
in species.
Using this relationship
and estimated rates of
tropical forest loss
Estimating Rates of Species Loss
The relationship between number of
species and area of habitat is S = c A z
the rate of loss of tropical forest from
satellite imagery is 1-2% annually
the resulting loss rate of species results in
an overall loss of 25 - 50% of the world’s
species by 2020
Assuming tropical forests harbor 10
million species, this loss is 27,000/yr (and
3/hr)
Summary
Biodiversity refers to the number and variety of
species, of ecosystems, and of their genetic variation
Some 1.4-1.8 million species are known to science.
Because many species are undescribed, some 10-30
million species likely exist at present
Biodiversity is threatened by the “sinister sextet”
Habitat loss represents the single biggest threat
Protected lands comprise about 5% of the earth’s
land area. Management of the remaining 95% must
also be part of a biodiversity protection strategy