Fishermen inspect monofilament fishing lines on Lake Victoria’s shore.

April 10, 2017

Cornell Researcher Explains Effect of Human Illnesses on the Environment

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Predictions of the likely effects of climate change are plentiful in scientific journals. Warnings of smog-engulfed cities, rising precipitation levels and the resultant changing landscape of diseases already seem to be realities in parts of the world. While the causes of such rapid change may be clear, one Cornell researcher believes that there is another avenue left to explore: the effect that human illnesses have on the environment.

“A lot of the ways that we’ve thought about this in the past is by considering how the environment affects our health. In this study we examine the other side: how our health might affect the environment. We aim to map out some of the pathways by which that might happen,” said post-doc Kathryn Fiorella.

To understand the cumulative effect of a sick community on the environment, Fiorella studied households around Lake Victoria, Kenya, where approximately 27 percent of adults are affected by HIV.

“We looked at a fishing community and studied how illnesses in people were affecting fishing practices. And what we found was that there wasn’t much of a relationship, as we expected, between illness and the amount of time that people spent fishing but there was some impact on if they were fishing at all. But for people who were fishing, the illness didn’t affect the amount of time they were fishing so much as the methods that they were using,” Fiorella said.

According to Fiorella, sick fisherman were more likely to use methods that were illegal or destructive to avoid physical exertion. Specifically, Fiorella noticed that fishermen were less willing to fish overnight or use methods that required them to enter deeper parts of the lake, focussing instead on fishing in ‘inshore’ areas. Consequently, they tended to use monofilament lines — that endanger fish and animals when discarded — to make it easier to catch higher quantities of fish. Such activities played a large part in decreasing the population of Nile perch in the lake by 65 percent between 2002 and 2014.

“One of the reasons for the high HIV prevalence around Lake Victoria is the migration that happened to harvest fish in the 1980s, a time at which HIV was starting to spread and there wasn’t much known about it,” Fiorella said. “A lot of inland fisheries throughout Africa have a high HIV prevalence. In these settings, people often face a range of other tropical illnesses as well, things like malaria and TB [Tuberculosis]. So in that sense, throughout the world, people who are charged with managing natural resources and rely on them face a high burden of disease.”

Fiorella emphasizes some important methodological choices made over the course of the study. Individuals were compared to themselves over different points in time, improving the inferences that could be made about their health and fishing behavior. As opposed to other common occupations, fishing was chosen because fisherman in the community frequently shifted their methods of fishing and studying the role that illnesses played in these shifts was thus, relatively easy.

“Illnesses may affect people through the physical dimensions of the illness and the way it affects people’s outlook. There are both of these possible pathways although we weren’t able to distinguish between them in our research,” Fiorella said.

Such effects are not limited to fishing. Similar observations have been made in agriculture, with a crucial difference. Illnesses had a greater impact on the time and effort people put in their agricultural livelihoods as opposed to the methods they used.

“Previous studies have been done with agriculturalists and have shown that when people are sick they reduce the time and effort they put into agricultural livelihoods. We studied fishermen and saw that the time they spend fishing is moderated by the method they chose and that illness is associated with switching fishing methods. The different timescales to harvest in agriculture and fishing might be a contributing factor to these patterns,” Fiorella said.

Fiorella hopes that the study will force people to consider a new angle in the ongoing debate about natural resources: the vulnerabilities of those tasked with managing them. She hopes that it will cause those in charge of health policy to carefully scrutinize their policies’ benefits as well as place a higher priority on providing better care and treatment to those managing crucial natural resources.

“We’re often very reasonably concerned about the effect of the environment on human health. Yet there may be a bigger cycle with feedback from human health to the environment too and that’s why pursuing this avenue is so valuable,” Fiorella said.