The importance of the Amazon’s small rivers

Cecília Gontijo Leal / RAS

By Cecília Gontijo Leal*

The Amazon rainforest is extremely diverse, even in its minutiae. The region’s small streams, known as igarapés, are proof of this: some have more species of freshwater fish than whole countries, such as Norway and Denmark. And if you imagine these strongholds of biodiversity as remote ecosystems in the heart of virgin rainforest, think again. All it takes is a few hours drive from the nearby state capital of Belém to the municipality of Paragominas, home to over 100,000 people, and intensive agricultural activity, to come across an igarapé capable of making the Scandinavians green with envy.

It’s also likely that just a few dozen kilometers further down the same road you’ll find another igarapé that contains a completely different set of species from the previous one, and often including species not found anywhere else in the Amazon. It happens that igarapés are extremely diverse in aquatic fauna and very distinct from one another.

There are still other reasons that justify their conservation. While the Federal Supreme Court in Brasília judges the constitutionality of the new Forest Code, altered in 2012, recent studies demonstrate that the Amazon’s small bodies of water are much more important than scientists previously supposed. While the loosening of regulations was already troubling based on the information available at the time, we now know that there is much more at stake.

In some drainage basins, igarapés represent 90% of the entire length of the waterways, in addition to being the heads of these intricate water networks. Interconnected via a single system, the igarapés suffer from the impacts of forest degradation, which then reverberate in larger rivers. These larger rivers, in turn, are already feeling the harmful effects of big infrastructure projects like hydroelectric dams.

The importance of igarapés and their high level of exposure to human activities, especially agriculture, were the themes of an article that we published in the scientific periodical Journal of Applied Ecology. Vital for the populations of the Amazon, igarapés provide potable water for human and livestock consumption; irrigation for valuable fruit and vegetable crops; fish for consumption and ornamental trade; recreation areas and navigation.

The preservation of a small number of igarapés located within protected areas created by the state, though fundamental, is not representative of their fauna as a whole, due to their biodiversity and singularity. On the other hand, it wouldn’t be viable for 100% of the igarapés to be contained within protected areas. Therefore, the solution is to guarantee their protection on private property as well.

Broadly speaking, the Brazilian Amazon is divided into protected areas and private property. In the private areas, the Forest Code is what counts. This legislation provides greater protection for riparian forests (vegetation along the edges of rivers, lakes and streams), considered permanent preservation areas. But this is practically the only consideration geared toward the protection of waterways in general.

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Cará (Aequidens pallidus, at left) and cascudo (Ancistrus sp., At right) in the Marupiara igarapé/bayou/stream, in Presidente Figueiredo (AM). Photos: Rafael Leitão / RAS

And the fact that specific legislation exists for these permanent preservation areas does not mean that their conservation is in good standing. Recent studies indicate that, in the past few decades, in Pará, riparian forests have suffered comparatively more deforestation than legal reserves (native vegetation more distant from the riverbanks), which demonstrates a failure to enforce the law.

The current version of the Forest Code, which reduced the size of legal reserves and permanent preservation areas and granted amnesty to deforesters, also opened up other loopholes. The first one allows for permanent preservation areas to also be counted as legal reserves when, in fact, the presence of riparian forest doesn’t substitute the need for forests located further from the bodies of water on the property – the igarapés need both.

The second loophole is that deforested legal reserves can be compensated by other areas in the same biome, preferentially in the same state. But the fact is that the Brazilian states in the Amazon are larger than many European countries and, in order to be effective, compensation needs to be truly local.

Lastly, there is also the matter of dirt roads. By cutting through the landscape with no planning and often times in a clandestine manner, they trample over the igarapés with poorly constructed bridges– uneven, makeshift shackles on the riverbeds–, interrupting the natural flow of water, as well as causing erosion and siltation. Though a single road crossing an igarapé might seem like a minor impact, the cumulative negative effects are significant. Our estimates suggest there are more than 3000 dirt roads crossing over igarapés in Paragominas alone. Imagine how many there are in the entire Amazon.

There is no doubt that the altered igarapés can generate local and accumulated effects of enormous proportions. And it’s not a question of blocking the development of Brazil’s agribusiness, but instead one of fueling the debate on suitable strategies for conservation and land use. Ultimately, Brazil’s environmental laws need to be strengthened and enforced. This is the only viable way to ensure a future for the Amazon.

* Cecília Gontijo Leal is a biologist at the Emílio Goeldi Museum of Pará and member of the Sustainable Amazon Network (RAS), an initiative comprised of over 30 scientific institutions in Brazil and abroad whose mission is to promote the conservation and sustainable use of the land in the Amazon.
This article was edited by journalist Thiago Medaglia. Founder of Ambiental Media and a former editor at the magazine National Geographic Brasil, Medaglia holds a graduate degree in Entrepreneurial Journalism from the City University of New York (CUNY).

How this article was produced:
The text is the fruit of a partnership between the Sustainable Amazon Network (RAS) and Ambiental Media, and was published in the newspaper Nexo on November 29, 2017. This content can be reproduced free of charge with credits held by Ambiental Media and the authors (text, photo, illustration, editing).