Rice fields are a prime example of contour farming. Courtesy of Shenghung Lin/flickr.

BOGOR, Indonesia (9 April, 2012)_Farmers toiling the slopes of Costa Rica’s Irazu volcano are using electric fences, improved pastures and practising ‘contour farming’ — planting crops across the slope — in their efforts to fight soil erosion and conserve water in a region that experts have declared is “highly vulnerable” to climate change.

“Soil erosion limits [farmers’] ability to reduce soil loss and, at the same time, can increase their demand on fertilisers and pesticides to compensate for degraded fertility,” warned Raffaele Vignola of Costa Rica’s Climate Change and Watershed Program (CATIE) and co-author of a study by the Center for International Forestry Research.

“Although some farmers are already using soil conservation practices, more understanding is needed to get them self-motivated in adopting such techniques, as a means of sustaining long-term food production.”

The volcanic soil of Irazu feeds nearly half of Costa Rica’s domestic demand for potatoes and vegetables. However the naturally sloping terrain is also exposed to extreme weather conditions, such as extreme rainfall, which exacerbates soil erosion. High water runoff can trigger the loss of the most fertile top part of soils and thus lessen its productivity in upstream areas, while the subsequent flow of sediment downstream can pollute the water table as well as affect drinking water quality.

The current situation in Costa Rica is already tenuous. According to Vignola, extreme rain has “significantly” increased in intensity and frequency, and experts predict it will likely worsen in the future — a particularly worrying prospect for an area where the unsustainable use of marginal lands is widespread.

Fuelling concerns are estimations by the Costa Rican Ministry of Environment which show that reduced soil fertility and soil erosion caused a 7.7 percent drop in the nation’s agricultural Gross Domestic Product from 1970 to 1989.

However there are a number of strategies available to farmers in Costa Rica to help reduce the negative impacts of agriculture on soil. Contour farming, the practice of tilling sloped land along lines of consistent elevation by creating furrows, crop rows, and wheel tracks across slopes, helps reduce the speed of water running downstream thus reducing its power to remove soil particles. This method also sees crop rows acting as reservoirs to catch and retain rainwater, thus permitting increased infiltration and more uniform distribution of the water. Electric fences can also make soils less susceptible to erosion by helping them control livestock movement thus regulating the weight charge that can compact soils.

While many farmers are already utilising these methods, Vignola and the other scientists stress the urgency of getting more people to adopt soil conservation methods. Despite some help from the government and private sector, more than 70 percent of those interviewed as part of the study admitted to not being involved in conservation programs.

But pushing the adoption of better soil management practices is easier said than done. According to the study’s results, farmers in the Birris watershed showed little awareness of the risks posed by the extremes of climate change on their soil, but were greatly concerned by the impact of human activities (i.e. agriculture and dairy cattle farming).

In spite of their anxieties, farmers with a higher perception of the risks were also those who were less likely to adopt conservation efforts. This, the scientists believe, comes down to a limited understanding of the consequences of their agricultural activities with daily exposure to erosion possibly giving the “illusion of control and/or smaller losses”. Some, the study said, were also deterred by fears of high implementation costs, especially for those harvesting smaller farmlands where a greater proportion of productive farmland might have to be dedicated to conservation.

“Perception of the problem is common, [and] the ability to address it is a function mainly of technical assistance,” Vignola said.

As such, the study argues that soil conservation programs should be strengthened to promote a better understanding of the causes, the consequences (on-site and off-site) and the limitation of soils and technological solutions in preventing erosion. It also advocates that technical assistance programs could help farmers improve their understanding of erosion causes which could, in turn, improve their chances of adoption.

“Education is related to knowledge of consequences of soil management practices and of alternative solutions, which in turn can influence behaviour,” Vignola said.