A new study demonstrates that the extraordinary breadth of fish species found in streams and tributaries of the Amazon isn’t afforded much protection from the effects of agriculture under current laws, such as Brazil’s Forest Code.
Such legal protections often focus on the vegetation found in forests, and they often address areas immediately around waterways, as well as the life found above the surface.
“When we think about Amazon biodiversity we tend to think of colourful birds, mammals, insects and amphibians,” said Cecília Gontijo Leal, an ecologist at Emílio Goeldi Museum in Brazil, in a statement. “But the small streams in and around the Amazon are also incredibly biodiverse.”
Nearly one out of every 10 fish species on the planet lives in the Amazon. Leal and her colleagues hypothesized that farming might be disrupting the habitats of many of these fish since streams flow through both protected areas and private areas, where the Forest Code typically calls for safeguards in the immediate vicinity of streams. The team looked at the potential impacts on 83 streams across Brazil’s eastern Amazon in 2010 and 2011, cataloging 24,420 individual fish representing more than 130 species.
“In just one [150-meter (492-foot)] stretch of one stream we found more fish species than are found in whole countries like Sweden or Denmark,” Leal said. “Some of them were new to science, and others were found in only a few individual streams.
“Many of these species could be at risk because of changes upstream that are beyond the reach of current conservation efforts,” she added.
The researchers found that the number of fish they encountered was affected by more than just the potential changes to the riparian environment or measurements of forest cover — which Brazilian legislation addresses. What had a greater effect on fish abundance were the changes to the “instream habitat,” such as water quality, the amount of shade and the substrate of the stream. Ways to mitigate these indirect human impacts aren’t captured by the current suite of legal protections in Brazil. They published their results online on Nov. 12 with the Journal of Applied Ecology.
The authors argue that conservation efforts must encompass entire basins and the complex drainage networks that together form the lifeblood of the Amazon rainforest.
“The health of small Amazonian streams depends on the health of the catchments they are part of,” said Toby Gardner, an author of the study and ecologist at the Stockholm Environment Institute, in the statement. “Forests far away from the margins are also important, as well as other factors that are overlooked in the legislation, such as dirt roads and agriculture intensification upstream.”
The scientists acknowledge the magnitude of the challenge, but also note that the implications of protecting these fish species extend beyond the bounds of the world’s largest rainforest.
“Our results highlight the complex challenges of conservation in tropical forest streams,” said co-author Paulo Pompeu, an ecologist at Brazil’s Federal University of Lavras, in the statement. “Protecting this biodiversity matters, not just for the Amazon but also for the world.”
Leal, C. G., Barlow, J., Gardner, T. A., Hughes, R. M., Leitão, R. P., Mac Nally, R., … & Ferreira, J. (2017). Is environmental legislation conserving tropical stream faunas? A large‐scale assessment of local, riparian and catchment‐scale influences on Amazonian fish. Journal of Applied Ecology, 1–15. http://doi.org/10.1111/1365-2664.13028
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