Experts link satellite imagery with socio-economic data

Experts link satellite imagery with socio-economic data

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US: By integrating remote satellite imagery with revelations from door-to-door interviews, Stanford University geographer Eric Lambin and his colleagues are exploring the complex conditions that give rise to a broad range of land-use challenges – from the reforestation of Vietnam to the spread of Lyme disease in Belgium.

Using satellite data, researchers have created maps of deforestation and other land-use changes over time. Satellites are precise tools, able to measure the rate of photosynthesis in a tiny clump of trees in the heart of the Amazon Basin. But satellite technology reveals little about the people living beneath the canopy who decide the fate of the trees around them. For a deeper understanding of how and why humans alter their environment, researchers need to talk face-to-face with the people who live there.

Through surveys and interviews, Lambin has uncovered the political, economic and social forces that contribute to the protection or destruction of forests and deserts across the globe. He first cast his magnifying glass on Vietnam. While studying reforestation trends in Vietnam, Lambin read in a newspaper article that the country’s furniture exports had quintupled from 1987 to 2006. He was mystified how a country with so little logging could produce so many couches and chairs.

He soon discovered that Vietnam wasn’t using less wood, just less native wood. It turned out that most Vietnamese timber was coming from neighbouring countries such as Laos or Cambodia, where environmental laws are more lax.

The results of the Vietnam forestry study could have a significant impact on international efforts to combat global warming, Lambin said. The ability to understand subtle land-use complexities, such as Vietnam’s illegal lumber trade, may determine whether such programmes succeed, Lambin said.

Lambin has taken his research a step further by exploring the relationship among land, humans and disease-carrying parasites such as ticks and mosquitoes.

In Belgium, Lyme disease is common among the urban middle class but rare among the rural poor, Lambin said. The ticks that carry Lyme disease run freely in parks and forests where people jog or bike but not in farmlands. However, Belgian farmers are more likely to contract a type of Hantavirus that lies in wait in soil dust, he added.

In northern Thailand, when loggers chop down trees, the forest opens and the puddles that breed malaria-causing mosquitoes evaporate, he said. When the deforested areas are converted into fruit orchards, the malarial mosquitoes are replaced by a different species that carry dengue fever – the leading cause of hospitalisation and death among Thai children.

Using satellite land-cover maps, epidemiological data and surveys of farming households, Lambin and his colleagues concluded that the shift from malaria to dengue fever was in large part caused by the presence of fruit workers in what had been a remote forest. “As you change land use, you’re changing the habitat of the mosquito,” he explained. “But most importantly, you’re changing where people go and at what time of the day.”

For Lambin, diseases are one more example of the complexities hidden within the static pixels of satellite images. “When you have so many variables interacting, the outcome is always contextual,” he said. “The time is ripe for an overarching theory of land change that explains the behaviour of people as well as land use.”

Source: Stanford University