Ecosystem with more species function better

Ecosystem with more species function better

By Nick Mawdsley

JAKARTA (JP): Three years ago, a unique meeting organized by
the United Nations in Rio de Janiero, Brazil produced commitment
from 157 of the world's governments to implement policies to
achieve sustainable development through the signing of the
convention on biodiversity.

This week Jakarta hosted the Second Meeting of the Parties to
the Convention of biodiversity where governments reviewed
implementation of conventions and addressed major scientific and
technical issues to achieve the highly desirable goal of the
sustainable use and conservation of biodiversity.

But just how much do scientists know about biodiversity and
its impacts on the world in which we live? More importantly, what
do we need to know?

The Global Biodiversity Forum, a companion meeting to the
conference and itself organized by a diverse array of
organizations was held prior to the conference. The forum
provided an opportunity for interested parties to air their views
on what exactly are the major issues relating to action required
to save and use biodiversity.

Forests hold much of the world's biodiveristy, and in a
workshop organized by the Bogor-based Center for International
Forest Research, forest scientists and conservationists
highlighted the need for greater information on the diversity and
distribution of forest species. Without this basic information,
conservation planning and the selection of protected areas simply
cannot be achieved.

Birds are perhaps the most well-known and best studied of all
groups, and Paul Jepson of the Birdlife International Indonesia
Program illustrated how the protected areas network in Indonesia
may be successfully improved through the establishment of
proposed protected areas in Maluku, selected using knowledge of
the global distribution of bird biodiversity.

Protected areas such as national parks are just one approach
to conservation, but with most land in much of Indonesia and
elsewhere being under agriculture and plantations, biologists and
conservationists are focusing on the potential biodiversity value
of these managed lands.

The vast, open landscapes of rice fields and modern single-
species tree plantations present perhaps the extremes of low
biodiversity value. Dr. Meine van Noordwijk from the
International Center for Research in Agro-Forestry in Bogor
showed the forum participants how other forms of land management
may preserve at least some biodiversity.

The center's researchers found that traditionally managed
rubber, durian and damar "agro-forests" do support a significant
proportion of forest species. Van Noordwijk suggested to the
forum that in some circumstances it might be better to integrate
conservation with agricultural production rather than segregate
the two.

Critical to this approach of integrating conservation and
agriculture is that agricultural methods become more
environmentally friendly using less fertilizer, less pesticides
and less extensive clearing of land, while maintaining adequate
yields.

The recovery of certain species in the British agricultural as
a result of less intense agricultural practices serves as a
lesson of how seemingly poor areas can be revived and made
valuable for nature conservation. Perhaps the largest area of
uncertainty concerning the conservation of forest biodiversity
raised by participants at the forum concerned the functional
significance of species.

What exactly do species do, and do we need to conserve all
species to keep ecosystems functioning properly? Ecosystem are no
different to towns and cities and their functioning depends on
water supply and flow, production of food through plant growth,
decomposition of waste materials and the renewal of nutrients. In
their totality these ecosystem functions enable natural and human
ecosystems to persist.

But prior to the 1980s, the significance of the variety of
species to the functioning of ecosystems was barely considered.
But then ecologists started to collect data and the answers they
found were surprising.

At Imperial College in England, ecologists led by Prof. John
Lawton create simple ecosystems using plants, insects and other
invertebrates commonly found in Britain. The ecosystems are
monitored by the researchers who make detailed measurements of
how each system functions together.

Contrary to the widespread belief that many species are
"redundant" to the function of ecosystems, the Imperial
researchers found that the ecosystems with more species
functioned better. Support for this unexpected result came soon
after from observations of North American grasslands carried out
by Prof. David Tilman. Tilman and his team found that grasslands
with most species were most resilient to a sudden and severe
drought. Again, it appeared that ecosystems with more species
were functionally better.

What then does this tell us about the most diverse ecosystems
on land, the tropical rain forests?

A single hectare of undisturbed lowland forest in Indonesia may
be home to over 200 tree species, and be used by up to 200
species of birds and 30,000 insect species -- more than are
present in the whole of Britain.

Do all these species contribute to the functioning of tropical
forests? Dr. Steve Compton from the University of Leeds said: "My
guess is that although tropical forests are complex, they
probably have a small proportion of species that are particularly
critical to their functioning. With the degradation of forests,
what is important in the long-term may not be the absolute number
of species retained, but whether the system contains these
keystone species or not." Indeed it appears that keystone species
do exists in some forests.

During periods of fruit scarcity in South America, fig trees
and palm nuts support populations of fruit-eating birds and mammals.
"Clearly if we lose the figs and palm nuts we may lose many
species that depend upon them," said Compton. "The consequences
for the forest of not having fruit-eaters is that seeds will not
be dispersed, which in turn may lead to a breakdown in the
ecosystem."

Such a drastic possibility demands identification and action to
conserve these keystone species, particularly as in many areas the
breakdown in ecosystem function may already have started.

Conservation managers and policy makers have the difficult task
of deciding the value of the less important species, but these
themselves may be valuable insurance policy in buffering
ecosystems against an unpredictably changing world. Despite these
concerns, the ultimate goal of conservation must be preservation
of the diversity of life.

As Prof. Lawton noted, "a species poor sanitized world may
work very well, but without wild orchids and orpendulas,
tardigrades and tigers, humankind will be the loser."

The writer is a professor at University of Leeds, England.