Conservation news

Communities on Brazil’s ‘River of Unity’ tested by dams, climate change

  • The Pixaim Quilombo is one of many traditional communities made up mostly of Afro-Brazilian descendants of runaway slaves. It sits at the mouth of the São Francisco River, one of Brazil’s most important waterways.
  • Once a thriving community, it has been struggling for decades due to the impacts of upriver dams which reduce the river’s flow and alter aquatic migrations. As a result, one of the community’s two chief livelihoods has been sharply curtailed — the river’s fishery is in steep decline.
  • Now, climate change threatens to make those struggles even greater, further changing fish populations, reducing river flow even more, and dangerously elevating the salinity of the stream as seawater intrudes. Rice, which once provided Paixim’s second major livelihood, can no longer be grown in the delta’s saltier marshes.
  • Pixaim is seeing a major outmigration as subsistence livelihoods becomes more difficult. Residents there count among 18 million people residing in the São Francisco River watershed, impacted by a steadily dwindling water resource.
The Piaçabuçu dunes, a unique geological formation, are classified as a protected area. Image by Sarah Sax.

PIAÇABUÇU, Alagoas state Brazil — The landscape where the São Francisco River enters the Atlantic Ocean seems so out of place it makes one wonder if this is still coastal Brazil. White sand dunes stretch as far as the eye can see; clusters of cashew trees throw flickering shadows like ocean waves on the sand.

Here among these shifting dunes escaped slaves in the 19th century hid from, and out-maneuvered, the Portuguese who came searching for them. Eventually, the formerly enslaved founded the Pixaim Quilombo near the mouth of the river and developed a reliable sustainable lifestyle and community well attuned to the dynamic, always changing estuary.

But it is a lifestyle utterly dependent on the São Francisco River; reliant on the planting of rice in marshes downstream and on catching plentiful freshwater fish upstream.

Now, varied and growing water demands by upstream dams and other users are threatening the long-established quilombo lifestyle — demands that experts predict will worsen severely in Brazil’s Northeast, one of the nation’s most climatically vulnerable regions.

“We used to catch fish that were meters long, but now you have to go much farther up the river to find them,” remembers 84-year-old Aladim, who lives in Pixaim and goes by his first name only. “The fish left, so the people left,” he remarks.

Aladim is an 84-year-old resident of Pixaim, one of Brazil’s remaining coastal quilombos. Seated opposite him is Marise dos Santos Lima, a tour guide who works for the Piaçabuçu Tourism Association. Image by Sarah Sax.

According to Aladim and Marise dos Santos Lima, a tour guide who works for the Piaçabuçu Tourism Information Association, about half of Pixaim’s population has already left for Brazil’s cities, as their two main livelihoods — fishing and rice cultivation — become more untenable.

“There used to be about 100 families, now there are only a few,” says Aladim. “You are lucky if you have a son and a grandson that stay.”

The lower stretch of the São Francisco River has suffered decreased flow for decades as hydroelectric dams, agribusiness and other interests have tapped into upstream waters. But a severe multi-year drought beginning in 2012, and considered one of the harshest in recent decades, if not of the last 100 years, has greatly deepened the estuary’s water problems.

The drought caused long periods of water stress, variability, and unpredictable levels and flows of the entire region’s rivers and reservoirs, leading to decreases in hydropower generation as well as rising conflicts between the agricultural and electrical sectors.

The drought reduced the water flow so much that, “the sea ate the river,” says Aladim.

“During the past decades, the São Francisco River basin has encountered substantial changes due to intensive human activities such as river regularization [channelization] and damming, and more recently, climate change,” explains Dr. Geórgenes Cavalcante, an adjunct professor of oceanography at the Federal University of Alagoas who has studied the river.

Decreased flow has radically increased the salinity of the lower stretch of the river, as the sea intrudes upstream, with potentially devastating effects on rice growing, fishing, the freshwater supply and public health. Aquatic ecology has suffered greatly, as fish and plant populations are displaced by salt and are replaced by opportunistic invasive species.

The Sobradinho dam on the São Francisco River. Image by water.alternatives on / CC BY-NC.
The Sobradinho reservoir. Water storage by the watershed’s many dams has greatly reduced flow and ended seasonal pulses that many fisheries species relied on. Photo credit: NASA Johnson on Visual Hunt / CC BY-NC.

“River of National Unity” reduced by drought

The São Francisco is one of Brazil’s most important rivers. It is the longest to lie entirely within the nation’s borders, running 2,700 kilometers (1,678 miles) from the central-south highlands of Brazil through the semi-arid and dry terrains of the Northeast, until it empties into the Atlantic. The São Francisco watershed drains 644,000 square kilometers (248,650 square miles), almost one-tenth of Brazil’s territory. The region is inhabited by 18 million people living in 503 municipalities along its main stem and tributaries, with shoreside urban areas including the country’s capital, Brasilia.

Known as the “River of National Unity,” it supplies irrigation water for an expanding fruit and vegetable industry, and a large freshwater fishery that provides food to millions; it is also vital for transporting goods and people.

Importantly too, it generates lots of hydropower — one of the most important of Brazil’s energy sources especially for the dry Northeast, which has grown particularly dependent on the São Francisco River. Over 40% of the installed electrical generating capacity in the Northeast comes from hydropower, and 86% of that comes from dams, including the Sobradinho, Itaparica, Complexo Paulo Afonso, and Xingó generating plants, all located on the São Francisco River.

Since the 1950s, the São Francisco River has seen the construction of several major dams, which now control 98% of the basin and have reduced discharge to the estuary by around a third — more in times of drought, which is intensifying as global warming escalates. The Xingó dam, 180 kilometers (112 miles) from the coast, and the last of the large dams to be built on the river, became fully operational in 1994. According to one study the seasonal discharge there, which previously fluctuated in a range from 800 to 8,000 cubic meters per second has been deeply cut to a constant flow of around 2,000 cubic meters per second.

“Dams always change the natural runoff on rivers where they are constructed,” says Dr. Mário Barletta, a marine ecologist at the Federal University of Pernambuco in Recife, Brazil. This can be especially detrimental for rivers that experience a lot of difference in their seasonal discharge, like the São Francisco. “ When you change the runoff, you change the entire ecological cycle. A lot of people end up being impacted by these changes, especially people that depend on these cycles like fishermen and shrimpers,” says Barletta.

Commercial fishing along the lower São Francisco River is one of the region’s main economic activities, but is threatened by low water flow, increasing salinity, and drought induced by climate change. Image by Sarah Sax.

Where did all the fish go?

The reductions, and erratic fluctuations, in river flow have significantly altered aquatic ecological conditions in the lower São Francisco River. Those changes have particularly harmed fish dependent on regular seasonal fluctuations. As a result, some of the stream’s species most important to traditional fishermen have been rendered locally extinct.

“Larger migratory species, such as the Surubim, the biggest fish of the São Francisco, simply disappeared from this region of the basin,” reports Dr. Paulo S. Pompeu, a biologist at the Federal University of Lavras who studies fish populations in the river.

Other studies likewise show a reduction of a variety of fish species as the result of impacts due to the dams. Far less clear is how, and whether, fishermen and the fishing industry can adapt, especially as drought strengthens its hold on the region.

“We can’t say that there are fewer fish than before, but there are definitely other fish,” says Dr. Igor da Mata Oliveira, a fisheries engineer at the Federal University of Alagoas, Brazil. “For example there is a fish in the lower São Francisco called ‘curmata’ (Prochilodus nigricens). This fish, 10 years ago, was the most important species for the fisheries. Now, we are observing that [this species, when compared to] all the freshwater fishing resources, represents less than 3% of the total volume landed.”

Rice used to be a major crop in the lower São Francisco River. Now, due to salt intrusion, coconut trees grow where rice paddies used to be. Seen here is a crumbling dike and abandoned rice paddy gate. Image by Sarah Sax.

A salty tale

Reductions in river flow have also caused greater intrusion of seawater.

Aladim remembers a time when he used to catch “sweetwater” fish in the river and plant rice in the marshes adjacent to the dunes. Rice cultivation was especially common along the last 15 kilometers (9 miles) of the river, he says, where the São Francisco’s waters spread out into a delta composed of fertile marshes, swamps, and lagoons — optimal for the grain.

“Ten years ago we used to still grow rice, but now, the water is too salty,” explains Aladim. Downstream from Pixaim, crumbling stone dikes are visible which once enclosed rice paddies. Instead, coconuts grow on the shores of abandoned marshes.

“Rice cultivation was very important traditionally, but rice doesn’t tolerate salt at all” notes da Mata Oliveira. “Because of the increase in salinity, rice cultivation has lessened, and coconuts have taken over.”

People from the nearby city of Piçabuçu are now seeing what Aladim has observed: while the river once flowed into the sea, the sea is now flowing upstream. “With the advance of the sea into the river, the flora and fauna have clearly changed. It is difficult to find freshwater fish in the mouth of the river, and freshwater vegetation can only be found when we go up the river, towards the source,” says Marise dos Santos Lima, a tour guide from Piaçabuçu who grew up in a traditional river community on the banks of the river.

The quilombo has adapted to the dune landscape using simple but innovative subsistence technology, like this well that filters water for drinking. However, climate change and rising ocean levels are causing salt intrusion into delta waters, and likely eventually into local aquifers. Image by Sarah Sax.

“High salinity affects large groups of organisms, from plants to fish, besides facilitating the introduction of invasive species,” Dr. Geórgenes H. Cavalcante, adjunct professor at the Federal University of Alagoas told Mongabay.

A 2020 study found that the reduction of water released from the Xingó dam, starting in 2013 due to increasing drought, has led to a marked increase in salinity 9 kilometers (5.5 miles) up from the river’s mouth. The levels of salinity in that stretch far exceeded the safe limits for human consumption, indicating that the delta water might no longer be a reliable source of drinking water.

These salinity levels impact the drinking water of Piçabuçu and other towns, which often increasingly have to put out boil-water and no-drinking advisories for groundwater supplies due to salt intrusion, says dos Santos Lima.

A Pixaim resident relaxes under the shade of a tree in front of his thatch hut in the midst of the dune landscape where his ancestors managed to live sustainably for generations. Now, climate change seems poised to depopulate the hamlet. Image by Sarah Sax.

Changing climate may spell disaster

While dams have had the largest impact on flow regimes so far, climate change is a deepening problem, according to several studies.

“Climate change plays a central role in this issue. Since rainfall in the [São Francisco River] basin is expected to decrease, changes in the river’s hydrological characteristics are likely to become even more severe,” says Pompeu.

By 2100, higher temperatures and significantly reduced rainfall patterns brought by global warming are projected for the Brazilian North and Northeast. Average annual rainfall could decrease there by up to 50% according to some models. Droughts from 2003 to 2016 have already led to 2,773 municipalities and more than 1,400 cities decreeing water emergencies — that represents almost 80% of the region.

Climate change will also seriously tighten its stranglehold on the São Francisco River in the year’s ahead, experts say, especially impacting its freshwater-starved lower reaches and delta. It’s very likely that drought could reduce hydropower production capacity in the region as well.

Two decades ago, in a book looking at the history and management of the river, one author wrote that “the challenge of meeting the multi-purpose demands for the water of the river system in a sustainable and environmentally acceptable manner will tax future thinkers and decision makers to the limit.”

That challenge is growing with each passing year. Options for managing the São Francisco’s diminishing flow equitably are running out, with relations between river communities increasingly strained and causing an ongoing debate in Brazil.

Part of the problem: water management is largely decentralized and regulated by the individual states under Brazil’s water law, so there is no overall regulating authority to fairly share out the resource, causing competition between states and municipalities.

In 2001, the São Francisco River Basin Committee (CBHSF) was created, composed of 62 representatives. That included a group representing traditional communities that technically should be able to add its voice to water use prioritization. But “The problem with the committee is [that] they are not invited to participate with the government of Brazil,” so have little real power, explains da Mata Oliveira.

The municipality of Piaçabuçu, (population 17,980) which sits 10 kilometers (6.2 miles) from the São Francisco River’s mouth, is similar to the Pixaim Quilombo in that both are heavily dependent on fishing as a livelihood, and both are threatened by climate change. Image by Sarah Sax.

In 2008, a program for the rehabilitation of the São Francisco River basin was created, even as then President Lula proposed a plan to divert more of the river’s water to the Northeast via the São Francisco River Water Diversion Project — the largest water infrastructure project ever attempted by the country, and parts of which are still under construction.

“Greater water release in the Lower São Francisco would imply less use for irrigation and energy generation in the upper parts of the basin. But this would [only] happen if environmental impacts are prioritized,” says Pompeu, who fears that escalating climate change will result in an ever-shrinking water supply — a pie to be divided in ever smaller slices among all the river’s many users.

“In a water scarcity scenario, it will be even more difficult to implement actions to return [the once great river] to natural conditions,” concludes Pompeu.

Banner image: Traditional fisherfolk on the lower stretch of the São Francisco River near where it flows into the Atlantic Ocean. Image by Sarah Sax.

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