Download Keystone species and Ecosystem

Keystone species and Ecosystem
In a population and ecosystem, describe/define the role that a keystone
species plays.
Hi,
I hope that the following will help you understand and be able to
formulate your answer to this problem.
Divide the word up in to two parts and it will give you an idea as to the
importance of this concept, crucial in today’s rapidly changing and
evolving environment with rapid depletion of resources, climate change
and rise in global pollution.
The word key can be used to mean central, important, vital.
The word stone is often used in terms of it’s signifiance e.g. foundation
stone, tomb stone etc.
Combine the words together had been done in terms of architecture and
the concept can be a valuable one.
I have included the definition from Wikipedia As follows:
A keystone species is a species that has a disproportionate effect on its
environment relative to its abundance. Such an organism plays a role in
its ecosystem that is analagous to the role of a keystone in an arch.
While the keystone feels the least pressure of any of the stones in an
arch, the arch still collapses without it. Similarly, an ecosystem may
experience a dramatic shift if a keystone species is removed, even
though that species was a small part of the ecosystem by measures of
biomass or productivity. It has become a very popular concept in
conservation biology.
An important point to stress would be that the species considered to be
the keystone in an ecological niche would not necessarily be the top
carnivore or the main producer etc, but the important feature is that
there removal has drastic consequences with the possible collapse of
the ecological niche or alternatively a drastic and dramatic effect on the
extent of the biodiversity. Where this impinges on human resources
particularly in developing countries that effects can similarly be
dramatic for human societies.
It is important to note that it may be an oversimplification of living
communities (or ecosystems), in which all species playsome role. It is
also not possible to identify keystone species in every ecosystem.
However the idea illustrates powerfully how the loss of a species from
an ecosystem (or the addition of a species that does not “belong” in that
ecosystem) can have a profound effect on how thatecosystem works,
often to the detriment of humans. The keystone species is often the “top
predator” in food webs, and so it is not surprising thatit has a profound
effect on the balance of numbers in species at lower levels in the webs.
There are good Scottish examples to illustrate this process. For
example, the extermination of the wolf in the late eighteenth century
removed the last predator of red deer. Today – helped by the way we
manage the land and by inadequate culling policies – red deer have
increased to huge numbers in many parts of the Highlands, causing
problems for farmers, crofters, grouse-moorowners and for the
conservation of our native forests and plant communities.If one species
becomes extinct, this can have a knock-on effect on others it interacts
with. Indeed, an analysis has suggested that the number of species
globally threatened with extinction is nearly 50 per cent higher than the
number currently listed as endangered. This is because the survival of
6,300 non-threatened species depends on the existence of threatened
species.
In other words Some species are — by virtue of their interactions with
others — important to the continued existence of their ecosystems.
These are known as 'keystone' species. The extinction of a keystone
species is predicted to cause a cascade of further extinctions.
In conservation biology, keystone species are ones which play a
central, critical role in ecosystems, and upon which many other
species depend. If an ecosystem can be returned to a state in which
the keystone species flourish, then all the other species which depend
on it will benefit as well. In the boreal component of the Caledonian
Forest, such as the pinewoods in Glen Affric, the Scots pine is a
keystone species. Therefore, by concentrating our efforts on Scots
pines, we find that the whole forest community begins to recover.
Another example of a keystone species, for riparian (or river-side)
ecosystems is the European beaver , which through its dam-building
creates micro-habitats of still water. These benefit certain fish species
and promote the growth of aquatic vegetation, which in turn provides
food for mammals such as the moose.
Some other examples that you will find in the literature include:
Limpets as keystone species of rocky shores because they keep algal
levels in check. They are not considered to be endangered.
The removal of starfish in certain ecological niches has been
responsible for collapse of some marine habitats
In his book,The Diversity of Life (Harvard University Press, 1992),
Wilson illustrated the idea with reference to the Californian sea otter,
which was hunted almost to extinction for its valuable pelt. Sea otters
(Enhydra lutris) were once found along the entire Pacific coast of North
America, but are now confined to California and Alaska. They were
huntedfor their valuable fur, and the Californian population was thought
to be extinct until a small group was discovered on a remote coast in
1938. With careful protection, numbers have built up to over 2,000 along
one stretch of the Californian coast.
Wilson wrote:–
“In places where sea otters disappeared completely, an unexpected
sequence of events
unfolded. Sea urchins, normally among the major prey of the otters,
exploded in numbers and
proceeded to consume large portions of the kelp and other inshore
seaweeds. In otter times, the
heavy kelp growth, anchored on the sea bottom and reaching to the
surface, was a veritable
forest. Now it was mostly gone, literally eaten away. Large stretches of
the shallow ocean floor
were reduced to a desert-like terrain, called the sea urchin barrens.”
In these sea urchin barrens, few fish could live and, as a result, many
inshore fishermen went out of business. The great fisheries and the
coastal canneries of towns like Monterey virtually disappeared, just as
the sea otter had done.
The sea otter story illustrates how easily marine ecosystems are
disrupted. We know least about how these ecosystems work, yet we
continue to over-exploit individual species from the seas. There are
already good examples of the complex impacts such exploitation may
have.
For example, overfishing of cod and other large predatory fish is
thought to have led to an increase in numbers of the smaller fish on
which they preyed. Some seabirds, such as the puffin, which feed on
smaller fish, may have benefited initially from these changes, and this
may explain recent increases in the size of some of their breeding
colonies.
Now, however, industrial fisheries increasingly are targeting smaller
fish, like sprats and sand eels. We have seen the impact of such
fisheries already on Norwegian islands such as Røst, where almost a
million puffin chicks starved to death during several summers in the
1980s because their parents could not find enough food to feed them.
CHECKSANDBALANCES
.
To quote Edward Wilson from his book The Diversity of Life (1992)
“Because scientists have yet to put names on
most kinds of organisms, and because they entertain
only a vague notion of how ecosystems work, it is
reckless to suppose that biodiversity can be
diminished indefinitely without threatening humanity
itself. . . . As extinction spreads, some of the lost
forms prove to be keystone species and trigger a
ripple effect through the demographies of the
survivors. The loss of a keystone species is like a drill
accidentally striking a power-line. It causes lights to
go out all over.”
CONSERVATION
Useful websites
http://www.snh.org.uk/pdfs/education/biodiversity/3%20keystone%20sp
ecies.pdf
http://www.treesforlife.org.uk/tfl.eco.html#3
www.abdn.ac.uk/biology/lectures/bi2001_foodwebs.ppt
http://www.scidev.net/ms/biofacts/index.cfm?pageid=423
http://en.wikipedia.org/wiki/Keystone_species
http://www.bbc.co.uk/nature/blueplanet/factfiles/molluscs/limpet_bg.sht
ml
http://www.pima.gov/cmo/sdcp/sdcp2/fsheets/key/key.html