Ancient fish farm revealed

The raised earth is seen throughout the landscape
Image: Clark L Erickson

By BBC News Online's Helen Briggs

New details of a "lost" landscape of earthworks covering hundreds of square kilometres in the Bolivian Amazon have been revealed by scientists.

Experts believe the large-scale earthworks are the remains of a fish farm that provided a food source for native people at least 300 years ago.

The zigzag structures cover 500 square kilometres (326 sq miles) of flat, seasonally flooded savanna near Bolivia's border with Brazil.

The weirs were probably used to trap and store fish to be eaten when the water subsided, according to the American and Bolivian archaeologists who carried out the new investigations.

A team led by Dr Clark Erickson, a curator from the University of Pennsylvania Museum of Archaeology and Anthropology in Philadelphia, US, documented a complex network of interconnected, zigzag structures of raised earth in the Baures region of Bolivia.

Fish traps

"We flew over the area in a small plane and I got a better sense of how big this whole network of these fish weirs (was), some of them interconnected, going from forest island to forest island, over this huge landscape," Dr Erickson told BBC News Online.

Fish weirs (darker green) covered with young and mature palms

The fish weirs have small funnel-like openings where the structures change direction.

Dr Erickson believes the openings were used to channel fish into traps. And ponds found nearby were probably used by native peoples as a fish store to provide valuable protein during the dry season, he said.

"In this case, they have solved this protein problem by managing the natural resources - not just fish but snails and palms that also produce a vegetable protein," said Dr Erickson.

The native peoples were later removed from the lands by Spanish missionaries and by European-introduced epidemics.

'Giant gardens'

But the researcher believes the abandoned earthworks still influence the vegetation, drainage and biodiversity of the region today.

Scientists have known about the Bolivian Amazon earthworks since the 1950s

"Humans have been altering, changing, constructing, transforming the landscape for a long, long time," he said.

"What we recognise out there as nature or wilderness in most cases is the product of thousands, and in some parts of the world, tens of thousands of years, of humans transforming the environment".

"We're finding more and more, at least in areas of the Amazon, that humans played an important role in the creation and maintenance of biodiversity."

"In a sense we're probably better to view these landscapes as giant gardens."

The research is reported in the scientific journal Nature.