Over The Horizon

Managing Wetlands with History

Ancient history may hold the key to the future survival of valuable wetlands in the Waikato, according to a Hamilton scientist.

Ninghu Su, a Chinese hydrologist recently arrived at Landcare Research's Environmental Quality unit in Hamilton, is making use of historical information to determine the impact of stresses and recovery rates on endangered inland wetlands around the Waikato, and work out how to conserve and manage them for the future.

One of the areas under the microscope is the Moanatuatua Bog, south of Hamilton, which has declined from 7,000 hectares to just a little more than 100 hectares since European arrival in New Zealand. A major fire in the area in 1972 has also affected the valuable wetlands resource, and the Landcare study will determine the effects of fire, drainage and discharge and nutrient fluxes responsible for the decline.

The research will also include measuring the recovery of vegetation around Lake Maratoto, which was accidentally burned early last year.

Ninghu Su was part of a major Australian research study on the environmental history of China. China, unlike most other countries, has continuous records going back more than 2,500 years of its water resource management which allow scientists to determine the effects of human impact on rivers and land.

Chinese philosopher Confucius kept records on bamboo, and early writings were kept on clay tablets before the use of paper. While several "cultural revolutions" led to the destruction of vital books, some records have also been kept in other Asian countries, providing continuous documentation on how past environments were changed by human intervention.

"Historical records of the country are `time series' data which scientists and historians can use to inform contemporary human beings of the environmental consequences of human intervention, and foretell people of some of the possible consequences."

For instance, he was able to search records to find that in 602 BC a dike of the Yellow River broke.

"Sediments and flood waters from the river were the worry and joy of the people living along the banks. The sediment eroded from the central plateau could be nutrients for crops to benefit people, or could be disastrous due to dike-break resulting from the sediment-elevated river bed in the rainy season.

"People built and also destroyed lakes, canals, roads, sea walls, marshes, landscapes and so on. People created their culture, history, society and environment and also changed the environment. Some of them were destructive, even disastrous."

Their research showed that from the late twelfth century to the late nineteenth century a change of course of the Yellow River caused such an extensive southward coastal shift of suspended sediments that it altered the geometry of Hangzhou Bay which lies in the south of the Yellow River estuary about 400 km away.

Ninghu Su says vital clues about the effects of modern human impact on a rapidly changing environment may lie in historical records. Science and history are more closely linked than many people believe, he says.

His work during his three year contract in New Zealand will cover three projects, including the wetland studies, and a study of chemical contaminants, water allocation and the effects of pesticides on the flat plains of Hawkes Bay.

While the study makes use of mathematical calculations and modern scientific technology, the clues to looking after the wetlands successfully in the future may be in the pages of history.