Is environmental legislation conserving tropical stream faunas?

The Amazon is a megadiverse biome of global importance, especially for forests and their animals. Less obvious is the importance of the hundreds of thousands of small streams that ramify through Amazonian landscapes and constitute up to 90% of the of the total channel length in some basins.

A new study published in the international scientific Journal of Applied Ecology brings to light the conservation relevance of the small streams in regions of agricultural expansion and shows that Brazilian environmental laws do not adequately consider stream biota. The research was carried out in 83 small streams (about 3 m wide) in two regions in the eastern Brazilian Amazon that comprise 60% forest cover, but also a great agricultural activity. The work is from the Sustainable Amazon Network, an initiative that draws together more than 30 institutions from Brazil and around the world to provide scientific information to assist the conservation and sustainable land use in the region.

Small streams in forest-agriculture Amazonian landscapes host a highly diverse fish fauna. In a single 150 m-stretch of stream, there were more species than in many entire countries, such as Norway or Denmark. Some species were new to science and many of them rare being only a few individuals or only in a few streams. Even in the one river basin, streams that are a few dozen kilometres from each other can have completely different sets of species. That means that keeping a few streams within protected areas is not enough to safeguard such biodiversity.

Dr Cecília Gontijo Leal, the lead author and a researcher at the Emílio Goeldi Museum in Brazil, explained “our study demonstrates that private properties are of great importance in ensuring conservation in the Amazon. Protected areas alone will not suffice to guarantee the conservation of stream fish. It is fundamental to enforce conservation measures aimed at small streams beyond parks and other public reserves.”

Legal mechanisms in Brazil in Brazil do not explicitly consider small streams and their associated fish and invertebrates, although the Brazilian Forest Code does protect the vegetation in the riparian zones along watercourses.

“The conservation of small Amazonian streams depends on the good functioning of the catchments of which they are part. That is, not only the deforestation in the margins brings consequences to the fishes”, says Professor Jos Barlow of Lancaster University in the UK, a co-author of the study. “Forests furthest from the margins are also important as well as other impacts not mentioned in the legislation, such as dirt roads and agriculture intensification” he concluded.

The results have important implications for the implementation of the Forest Code in the Brazilian Amazon. The law allows a deforested area in a given property to be compensated anywhere in the biome. However, the new study underscores the importance of local compliance either by focusing on rehabilitation in landscapes that are heavily deforested or by undertaking off-farm compensation within the same river basin. The authors empahisized that the focus of the Forest Code on riparian forest patches should not neglect the need to maintain and restore native vegetation in areas further away from the streams.

Professor Ralph Mac Nally, from the Institute for Applied Ecology and a co-author on the study, commented “Australia’s conservation management agencies need to draw messages from this work. Up until now, terrestrial and freshwater ecosystems have tended to be managed separately, with little recognition of their interdependence. This pivotal work in Amazonia clearly shows the need for a unified management approach to whole catchments and river basins to effectively conserve our plants and animals.”

Read the full article here.