New study finds clearing riparian forests may significantly impair the structure and function of rivers
A soy field abuts a forest surrounding a river in Mato Grosso, Brazil. Photo by Rhett A. Butler.
Vast areas of the Amazon forest are being destroyed for agricultural uses, mainly industrial-scale soybean crops, and turned into pasture land for livestock. The riparian forests surrounding streams have not been exempt from this trend. And though headwater streams in the Brazilian Amazon are valuable aquatic ecosystems, little research has been done to determine how deforestation is impacting the streams’ environmental integrity and ability to function as natural habitats.
That is, until now. A study by researchers in Brazil published this week in mongabay.com’s open-access journal Tropical Conservation Science has found that “altered streams” in the Southern Amazon–i.e., those located in forests that have been degraded or destroyed–have lower oxygen concentrations, an average increase in water temperature of 1 degree Celsius, and less available organic material.
In other words: deforestation is degrading the habitability of Amazonian streams, and this could have impacts beyond just riparian zones.
Cattle ranching is a primary driver of deforestation in the Brazilian Amazon. Photo taken in Mato Grosso by Rhett A. Butler.
The study’s lead author, Monica Bleich of the National Institute of Amazonian Research, told mongabay.com that she was surprised by the severity of the impacts of deforestation on the 10 Amazonian sites her team studied, and that these effects could certainly be felt more widely. “Considering the high density of headwater streams in the Amazon,” Bleich said, “the degradation of these ecosystems may impair significantly the structure and function of large [Amazonian] rivers.”
Bleich and her team of researchers studied 10 sites in Mato Grosso state in Brazil. At each site, they selected one pristine headwater stream and one with riparian deforestation and took three sets of samples between July 2010 and May 2011.
Amazonian aquatic ecosystems vary throughout the dry and rainy seasons, so the researchers tracked habitat conditions at different stages of the water cycle. What the study found was that partial or total deforestation of Southern Amazonian riparian forest leads to “loss of variability in headwater stream habitat structure across hydrological periods, making habitat conditions more homogeneous and simplified throughout the year.” A simplified habitat is less capable of sustaining an abundance of life.
Bleich says that these results not only show that it is necessary to preserve riparian forests, but also that the rehabilitation of degraded riparian areas is essential to ensure that aquatic ecosystems provide a suitable habitat structure for wildlife that rely on headwater streams for food and shelter.
According to the study, however, there are significant hurdles to accomplishing the necessary conservation and rehabilitation measures: “a paradigm shift is necessary to conserve the Amazon, one that expands the focus beyond the forest to aquatic ecosystems,” the authors write. “Restoring the structural complexity of altered streams is a great challenge, as it requires more than simply introducing physical elements into stream channels or planting tree species in the riparian zone.”
According to Global Forest Watch data, Mato Grosso lost 7.9 million hectares of forest—nearly 14 percent of its forest cover—between 2001 and 2012. The study states mining and logging have been damaging rivers in the area since the 1970s, with cattle ranching becoming a primary driver of deforestation in the 1990s.
With 7.9 million hectares of tree cover lost from 2001 through 2012, Mato Grosso has only a relatively small portion of intact forest left. Map courtesy of Global Forest Watch. Click to enlarge.
The research team studied Amazon tributaries in the northern portion of Mato Grosso, an area heavily affected by clearing. Map and satellite image courtesy of Global Forest Watch and Google Earth. Click to enlarge.
Citations:
Bleich, M. E., Mortati, A. F., André, T. and Piedade, M. T. F. 2014. Riparian deforestation affects the structural dynamics of headwater streams in Southern Brazilian Amazonia. Tropical Conservation Science Vol.7 (4): 657-676.
Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. “Hansen/UMD/Google/USGS/NASA Tree Cover Loss and Gain Area.” University of Maryland, Google, USGS, and NASA. Accessed through Global Forest Watch on Dec. 18, 2014. www.globalforestwatch.org.Related articles
Plant wars: some tree species compete better against grasses for reforestation
(12/18/2014) What happens to degraded pastureland once the cows are kicked out? After years of letting the area rest, does it eventually become what it once was? Not likely. When disruptions such as invasive species and human interference are introduced to an area, ecological succession doesn’t occur the way it should naturally.
Scientists reintroduce agoutis in rainforest in city of 12 million
(12/17/2014) When one thinks of Rio de Janeiro, one usually doesn’t think: rainforest. However, in the heart of the city sits a massive rainforest sprung over long-gone sugar and coffee plantations. The forest—protected today as the Tijuca National Park—is home to hundreds of threatened species, but no agoutis, a common ground mammal in Latin America.
An app to save 400 million animals
(12/11/2014) Brazilian biologist Alex Bager has been leading a crusade to raise awareness of a major but neglected threat to biodiversity in his country. Every year over 475 million animals die in Brazil as victims of roadkill, according to an estimate by Centro Brasileiro de Ecologia de Estradas, an initiative funded and coordinated by Bager. This means 15 animals are run down every second on Brazilian roads and highways.
False victories for sustainability – Amazonian Hydropower
(12/09/2014) Dams are hugely controversial, especially in the Amazon Rainforest. Their proponents, flashing green credentials, have dammed the tributaries of the Amazon for decades. However, there is a rising backlash against the huge economical, environmental, and sociological costs dams bring. A paper led by Dr. James Randall Kahn from Washington and Lee University is the latest in this volley.
New endangered bird species discovered in Brazil
(12/04/2014) The Bahian mouse-colored tapaculo (Scytalopus gonzagai) has only just been discovered by scientists in the heavily logged Atlantic Forest of southeast Brazil — and it’s already believed to be endangered.
Threatened indigenous forests store more than half the Amazon’s carbon
(12/02/2014) A new study released today finds the total carbon load locked up in parts of the Amazon rainforest held by indigenous groups to be much higher than previously estimated – an amount that, if released, would be capable of destabilizing the earth’s atmosphere. But because of flimsy land rights, these areas stand at risk of deforestation.
Amazon deforestation in Brazil drops 18% in 2013/2014
(11/26/2014) Figures published Wednesday by Brazil’s National Space Research Institute (INPE) show that 4,848 square kilometers (1,871 square miles) of forest — an area about the size of the state of Rhode Island or the country of Brunei — were cleared between August 2013 and July 2014.
Rising deforestation, fossil fuels use drive Brazil’s emissions 8% higher
(11/24/2014) Brazil’s carbon emissions jumped 7.8 percent in 2013 due to rising deforestation and fossil fuels use, according to data released by Observatório do Clima (Climate Observatory), an alliance of mostly Brazilian non-profits.
Brazilian government silent as deforestation rises in the Amazon
(11/17/2014) Deforestation in the Brazilian Amazon continues to outpace last year’s rate by a significant margin, reveals data released today by Imazon, a Brazilian non-profit. Imazon’s analysis of satellite data shows that for the 3-month period ended October 31, 2014, deforestation is running 226 percent of last year’s rate. Forest degradation, which often precedes outright clearing, is pacing 691 percent ahead of last year.
Greenpeace investigation prompts Belgian authorities to seize timber shipment
(11/16/2014) Authorities in Belgium seized two containers of Brazilian timber in Antwerp following a demonstration by Greenpeace, which alleged that the Ipe timber had been cut illegally and therefore violated the EU’s trade laws.
New tapir? Scientists dispute biological discovery of the century
(11/13/2014) Nearly a year ago, scientists announced an incredible discovery: a new tapir species from the western Amazon in Brazil and Colombia. The announcement was remarkable for a number of reasons: this was the biggest new land mammal discovered in more than 20 years and was only the fifth tapir known to the world. But within months other researchers expressed doubt over the veracity of the new species.
New laws may turn Brazil’s forests into mines
(11/07/2014) With the world’s largest system of protected areas and a 70 percent drop in the deforestation rate of the Amazon over the past decade, Brazil has made huge strides in safeguarding what’s left of its wilderness. However, this progress now hangs in the balance, with new laws threatening to turn many of the country’s protected areas into mines and dams.
