Gardens - Friday 16 August 2013

We've now finished our fieldwork! Time to pack up and think.

Reflecting on the week, and discussions on the island, I'd like to talk about Polynesian agriculture. Agriculture perhaps doesn't compete very well with the mysteries of moai for attention. But every story of moai has to feature how successful agriculture must have been to allow all those people to focus so much labour on building and moving moai. Let's focus on agriculture. Everyone loves a good garden!

The story of collapsing agriculture and soil erosion on Rapa Nui appears to be greatly exaggerated. A recent book by New Zealander Rhys Richards provides abundant evidence from previously unknown ship's logs (in maritime museums around the world) that agriculture remained highly successful on the island up through the period around 1864 when the island's population was decimated by disease. Abundant crops from healthy and extensive gardens were usually available for trade. An extensive 1864 letter from the first European missionary on the island, Eugenio Eyraud, emphasises that plants grew almost effortlessly, especially kumara (sweet potato). 

The key to agriculture, with crops coming from the humid tropics to relatively cool and dry subtropics was to maintain soil warmth and stop water loss. The cool temperatures we experienced this week (average daily high 22°C or 71°F) emphasise that Rapa Nui is cool in winter! Stones provide the perfect means to soak up heat, and also stop water loss from soil.

Since our last visit, there has been a lot of experimenting and demonstration of rock gardens, including mana vai and lithic mulch. Sonia took us to some gardens she created at the local high school, and along one of the main roads. All were impressive. 

A tiny taro plant, emerging from rocks.

Most impressive of all was the story of paired plots of taro. Taro is a root crop from the lily family, with leaves that grow as tall as a person when it is healthy. One plot was grown without stone mulch, and the other plot with stone mulch. After a year, both were harvested by the Earthwatch volunteers. The stone crop was much bigger, juicier, and healthier. Quantitative results, including nutrition testing, are part of the project.

I'm impressed with the emerging story of gardening. Most of all, the use of rocks and written evidence of health agriculture should make us all question the exaggerated stories of soil erosion that supposedly led to collapse after deforestation.

A variety of kumara (sweet potato) from Tahiti, growing in the school garden.

Bananas in a mana vai (enclosed rock garden).