When it comes to deforestation, wood and water issues are often looked at in isolation. However, a pioneering study by researchers at Virginia Tech University has shown for the first time that there is a significant link between deforestation and reduced fish catches.

The connection comes down to food. Leandro Castello, assistant professor of fisheries at Virginia Tech, says: ‘Floodplain forests are the principal sources of food [for fish] via provision of detritus, tree leaves, fruits and insects.’ Indeed, for the economically important tambaqui fish (pictured above), which can fetch top prices in fish markets, fruits and seeds constitute the major food source during high waters when the species can enter new territories to feed and spawn. Deforestation, it seems, removes not only these food sources, but also the habitats that protect fish and their offspring from predators. ‘It shows that tropical deforestation is not just an issue that affects climate change or terrestrial biodiversity,’ says Castello.

 The research analysed floodplains over a 400-square mile area of the Amazon and 12 years of regional fishery data. This was combined with land cover maps from satellite images showing the amount of woody habitat in the floodplains. The two sets of data showed the connections between the amount of fish in the Amazon’s lakes with the amount of forest around each of them. Castello’s team found that deforested areas matched with local fisheries producing much lower yields than those with larger forest areas surrounding them.

If fish do depend on forests, the link is bad news for fisheries all over the tropics. According to the report, these areas are not only some of the most productive food sources, but often sustain livelihoods of the poorest human populations. Compared to uplands, however, there are fewer protections in place for floodplains. Many are at risk of alteration. In the area studied, 56 per cent of the forests have already been cleared to make way for cattle ranches and plantations in recent years.

‘More strict legislation is necessary to protect floodplain forests from clearing to do ranching or agriculture,’ says Castello. ‘Even if cattle ranching provides more cash in the short-term, it is unlikely that such benefits will be greater than the overall food, income, and livelihood security that come from fisheries in the long-run.’

This was published in the February 2018 edition of Geographical magazine.

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