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.