VANCOUVER – An ancient wetland-gardening site unearthed during a road-building project in British Columbia is as culturally important as any other wonder of the world, says a member of the indigenous group who directed the excavation project.

A study published Wednesday found that as early as 1,800 BC, ancestors of the Katzie First Nation in B.C.’s Lower Mainland were engineering the wetland environment to increase the yield of a valuable, semi-aquatic plant known as a wapato. The report describes the finding as the first direct archeological evidence of the cultivation of wild plants in the Pacific Northwest.

“This is as important to us as the Egyptian pyramids, or the temples in Thailand, or Machu Picchu,” said Debbie Miller, who works with an archeological consulting firm owned by the Katzie Nation.

Road building crews uncovered a rock platform measuring about 12-square metres made up of flat stones that would have rested several feet underwater four millenniums ago. The distribution of the stones into a pattern of single and double layers, as well as their closely packed arrangement, suggests they were placed deliberately, the study published online in ScienceAdvances found.

The stone “pavement” would have prevented the wapato from penetrating deep into the sludgy, wetland sediment, making it easier for gatherers to use long, sharpened digging tools to locate the buried plant and cut it free.

Wapato, which is a tuber, is a semi-aquatic species that was prized as a valuable trading commodity and served as an important source of starch over the winter months.

The site is in Pitt Meadows, about 40 kilometres east of Vancouver.

Besides the more than 3,700 pieces of plant material recovered from the site, excavators found more than 150 fire-hardened tips of what are believed to have been digging tools.

The region’s inhabitants are believed to have abandoned the plot about 3,200 years ago, after which researchers discovered the site soon acidified and dried up, Miller said. This, along with sedimentary analysis, suggests First Nations gardening techniques contributed to the overall health of the wetland ecosystem, she added.

Miller said most of the 90-person crew who worked on the archeological project were members of Katzie First Nation and that many were young people who were able to use the project to better connect with their heritage.

“Culturally we talked about what it meant to be in the earth with our ancestors and touching their lives,” she said.

“We’ve just walked in the house of the ancestors. It was for many, many of our people an absolute connection to their history, something that they couldn’t have gained in any other way.”

Miller explained that First Nation legend has the character Swaneset going to the other world and returning with a wife, who brought with her the wapato, which became one of the most prevalent resources in the territory.

But the discovery of the wetland garden was also a bittersweet one for the Katzie people, Miller said. Once the excavation was complete, the site was paved over with a public road.

“We brought our ancestors home in our hearts and in our minds and in our conversations with our people,” she said, her voice cracking.

Other examples of First Nations managing non-domesticated plants include constructing clam gardens along the Pacific Northwest, maintaining fruit and nut trees in the eastern woodlands, and building fish and eel traps in Australia.

— By Geordon Omand in Vancouver. Follow @gwomand on Twitter.