July 12, 2016 by Claire
Salisbury, Mongabay Series: Amazon Infrastrure
Extensive Series of Photos Posted
Throughout Article
The Amazon Basin boasts 17
species of turtle, including the Giant Amazon River Turtle (Podocnemis expansa). All are under
pressure and in need of conservation.
Amazon turtles imperilled by
dams, mercury pollution and illegal trade
The Brazilian Amazon is home to
17 turtle species, all of which are under pressure from overexploitation, the
illegal wildlife trade, widespread hydropower dam construction, and mercury
contamination. Deforestation, agricultural development and climate change are
other looming threats.
The Brazilian government’s Amazon
Turtle Program focuses its conservation efforts on the Giant Amazon River
Turtle (Podocnemis expansa), plus the
Yellow-spotted River Turtle (P. unifilis),
and Six-tuberculed River Turtle (P.
sextuberculata). The Wildlife Conservation Society works with these same
species and is also conserving the Red-headed Amazon River Turtle (P. erythrocephala), and Big-headed
Amazon River Turtle (Peltocephalus
dumerilianus).
Amazon dams — especially
mega-dams like the just built Belo Monte dam and the proposed Luiz do Tapajós
dam — alter ecosystems and disrupt the annual flood cycles that inundate
lowland Amazon forests, putting turtles and other species at risk.
Mercury contamination of Amazon
rivers due to illegal gold mining is a major threat to turtles. Researchers say
there is an urgent need for the Brazilian government to develop and implement
guidelines for the assessment of mercury toxicity in Amazon reptiles,
especially turtles.
For as long as people have lived
in the Amazon, turtles have likely been on the menu. But what was once
low-impact subsistence hunting escalated dramatically after the arrival of
Europeans. From the 1700s onward, demand for turtle eggs and meat skyrocketed.
And the eggs weren’t just for eating: estimates suggest that more than 200
million eggs were harvested for both consumption and oil, fuelling lamps across
Europe for two centuries.
This overexploitation led to such
dramatic population declines that the Brazilian government eventually stepped
in, launching the ambitious Amazon Turtle Program in 1979 — an on-going
initiative that has so far protected 70 million turtle hatchlings across the
Brazilian Amazon, with the intent of conserving vulnerable species.
But while that program continues
to work toward a sustainable future for turtle populations —and for the people
who still see chelonians as an important source of protein — three more recent
threats loom over Amazonian turtle species: the illegal wildlife trade,
widespread hydropower dam construction, and mercury contamination.
Turtles at risk
The Brazilian Amazon is home to
17 turtle species that occupy important ecological niches in freshwater
habitats ranging from main river channels, to flooded forests and lakes.
The largest neotropical
freshwater species, the Giant Amazon River Turtle (Podocnemis expansa), is also at the heart of chelonian conservation
efforts. Weighing up to 65 kilograms (143 pounds), P. expansa is a species of side-necked turtle — retracting its neck
horizontally as opposed to vertically like other species. It has a large domed
shell adapted to swimming in river currents, but it also inhabits lakes and
flooded forests during the rainy season. When it’s time to lay eggs, the
turtles move en masse to their nesting beaches. Recent research has found that
the species uses several vocalizations to communicate during this time,
including between mothers and offspring before and after hatching.
Unfortunately for P. expansa, its longevity and late
reproductive maturity, coupled with the species’ predictable mass nesting
behavior on exposed sandbars and beaches, make it especially vulnerable to
hunting and egg-harvesting pressures.
Historical accounts relate how
the Amazon’s Madeira River used to became so congested with nesting turtles
that boat traffic was impeded, even as many thousands more nesting turtles covered
river beaches as far as the eye could see. These turtle tales seem almost
unbelievable now; the Giant Amazon River Turtle was listed as Endangered by the
IUCN in the 1980s, though it has recovered some since, thanks to persistent
conservation efforts.
The greatest threats to Amazonian
turtles today are “dams and people collecting them to sell in large cities,”
Richard Vogt, of Brazil’s National Institute of Amazonian Research (INPA), told
Mongabay. Camila Ferrara, of the Wildlife Conservation Society (WCS) Brazil,
cites “uncontrolled consumption of eggs and meat” as the biggest threat, even
though prohibited by law, unless authorized by IBAMA, Brazil’s environmental
agency.
Ferrara notes that these
immediate pressures exist within a broader context of deforestation, increasing
agricultural activity, and climate change. “We already know that dams and
global warming are threats, but we do not know yet all the consequences,” she
said.
From overexploitation to
conservation
The Amazon Turtle Program has been
a champion of chelonian conservation for nearly forty years. Today, its primary
target species for preservation include the Giant Amazon River Turtle, along
with several related species within its biological family, including the
Yellow-spotted River Turtle (P. unifilis),
and Six-tuberculed River Turtle (P.
sextuberculata).
The Wildlife Conservation Society
(WCS) also works with these species, as well as with the Red-headed Amazon
River Turtle (P. erythrocephala), and
Big-headed Amazon River Turtle (Peltocephalus
dumerilianus). WCS is working in protected areas on the Purus and Negro
rivers, where its goal is to reduce overexploitation by finding ways for
turtles and people to live together, Ferrara said. Participative programs
launched in communities along the Rio Negro — where locals get involved in
protecting nests and monitoring populations — are showing promise.
The Amazon Turtle Program’s
geographical scope is much broader. It has targeted hundreds of breeding
grounds across the Tocantins/Araguaia and Amazon River basins.
“The program tries to protect
some of the main nesting areas of [the target species] during the reproductive
period,” Roberto Lacava, coordinator of the program at IBAMA, told Mongabay.
Some 800,000 females have had their nests protected over the project’s history.
“In the last years, we released around 2.5 to 3 million hatchlings [annually],”
he reported. Most hatchlings are produced and released on the protected
beaches, though in some special cases the nests are relocated to better protect
the eggs until they hatch.
Though this may sound like a
staggering number of animals to have been released, Vogt, who has been studying
turtles in the Amazon for more than 25 years and is an advisor to the Amazon
Turtle Program, puts these totals in context: “These are not huge numbers,
considering the vast size of the Amazon Basin,” he explained. “Also the
survivorship of hatchlings is low, [so] only a small portion of these [young
turtles] reach maturity.”
“Releasing hatchlings in some
areas has been beneficial, and populations of adults have been increasing,”
Vogt noted. Results have been so good, in fact, that the Giant Amazon River
Turtle is no longer considered Endangered, and is now classified as low risk
but dependent on conservation activities. “We only do headstarting [nest
protection and the release of juveniles] with hatchlings in a few places, where
the population is in danger,” Lacava revealed. “We don’t consider [it]
necessary to continue releasing turtles in most of the areas.”
The Amazon Turtle Program is now
focused on regions where the turtle situation has not improved, or is getting
worse. In those areas “the adult population keeps going lower because of the
continual poaching threat,” Vogt said, a problem that persists due to lack of
law enforcement. “Nothing is done to stop poachers; they are captured and
released and never pay fines,” he laments.
Larissa Schneider, of the
Australian National University, has been studying Amazon turtles for over a
decade; she too sees poaching as a serious problem. “The main threat affecting
Amazon turtles is still the black market, and uncontrolled smuggling of
turtles. The Brazilian government has been ineffective at curtailing this
activity,” Schneider declared. Wildlife smuggling is the third largest form of
illegal trafficking in Brazil, following drugs and firearms, and it accounts
for billions of dollars in illegal trade annually, she said.
Despite these ongoing challenges,
Lacava sees Brazil’s turtle conservation efforts so far as a success,
“Although,” he adds, “we have a long way to go.”
Dams and turtles don’t mix
Combatting overexploitation is
just one part of the turtle conservation challenge. With hundreds of
hydroelectric dams already up and running, under construction or planned across
the Amazon, numerous aquatic and terrestrial species are seeing their habitats
lost or degraded.
Dams disrupt the annual flood
cycles that inundate lowland Amazon forests. Reservoirs permanently flood vast
areas, and species movements are prevented. Some species are even in danger of
extinction as a result.
For turtles, the most obvious
impacts of dams are the disruption of migration routes, and the loss of nesting
beaches as reservoirs fill with water, and the flow of rivers is altered
downstream.
Lacava explained that interrupted
migration during reproductive periods “could cause a severe interference in the
genetic structure [of turtle populations], especially for P. expansa.” The
isolation of populations by dams, as also seen among Amazon river dolphins, can
make sub-populations more vulnerable to additional threats.
“Another impact is the change in
the river flood regime, causing the disappearance of nesting beaches and the
loss of many nests,” due to flooding, Lacava said. But he emphasized that more
data is urgently needed to understand these effects, especially
species-and-dam-specific studies that could reveal the full implications of
Amazon dams before they are built.
Most of what scientists know about
the likely impacts of future dams on turtles comes from two of the oldest
Amazon mega-dams, Balbina and Tucurui, Schneider said. Balbina dam, built in
the late 1980s on the Uatumã River to provide power to the city of Manaus, has
an installed capacity of 250 megawatts, and flooded 2,360 square kilometres
(910 square miles) of forest. Construction of the 8,370 megawatt Tucurui dam on
the Tocantins River began in 1974, and inundated 2,850 square kilometers (1,100
square miles).
Vogt has been involved with
turtle mitigation activities at Balbina, a dam that has caused serious problems
for turtles. “When the Balbina dam was closed, 65 adult females were [isolated]
behind the dam,” Vogt said. “They now nest on the only available beach [there],
an island which was too cold [due to shading], so none of their eggs hatched.”
Providing artificial nesting
beaches, however, proved to be a partial solution: We built “nesting beaches
just below the dam, one of coarse sand for P. expansa and the other of fine
sand for P. unifilis. The turtles migrating up to the dam use these nesting
beaches. They have been washed out at least once and built up again, [but] they
work,” Vogt said.
Further insights regarding
Balbina and Tucurui turtle impacts paint a more troubling picture, as Schneider
elaborated. “Essential micro-habitats used by turtles are lost in water
impoundments including dams, weirs and barrages. Impoundments make juveniles
particularly vulnerable due to loss of sheltering sites, loss of important
prey/food species, and cooler water temperatures.
“The food chains of turtles are
fundamentally different in lakes than in rivers,” Schneider continued.
“Amazonian turtles that rely on cloacal respiration [breathing underwater via
the single rear opening of the digestive and reproductive tracts] are
disadvantaged in the stratified, low-oxygenated, turbid water in impoundments.”
The larger the dam, the greater
the impacts, so mega-dams pose the most serious threats. For new mega-dams,
such as the just completed Belo Monte dam and the proposed São Luiz do Tapajós
dam, “turtles have already been [or will be] detrimentally affected by
impoundments due to the loss of riffle habitats [shallow, fast-flowing rapids],
and the disappearance of food items such as aquatic plants (macrophytes), the
loss of windfall fruits from riparian vegetation as well as some aquatic
invertebrates,” Schneider said.
“Changes in water quality is also
a straight forward impact faced by turtles right after dams are built. We can
anticipate that long-term problems from Balbina and Tucurui will most likely
affect the new dams as well,” she concluded.
Concerns are emerging that the
Belo Monte dam over the long term may threaten one of the most renowned of
annual Amazon natural spectacles — the arrival of 20,000 Giant Amazon River
Turtles to lay their eggs at the Tabuleiro do Embaubal, a stretch of sandy
beach on the Xingu River. Biologists fear that the dam, located upstream from
the nesting area, will prevent the replenishment of sand during the rainy
season, eventually causing the beaches to vanish, leaving the turtles no place
to deposit their eggs.
Mining and mercury
As if all those obstacles to
turtle survival weren’t bad enough, hydropower and the extractive industry are
inextricably linked in the Amazon, causing more habitat and species harm.
Bauxite, nickel, and copper mines that benefit from the power that dams
generate cause habitat destruction and lead to human population migration into
remote regions, which results in increased pressures on the natural resources
in the vicinity of mining operations.
But an invisible, insidious
consequence of mining is of particular concern for turtle species, and to
anyone who eats turtle meat and eggs: mercury contamination caused by illegal
artisanal gold mining.
“Hg [mercury] causes adverse
effects on turtles, such as behavioral and endocrine disruption, and at high
concentrations can be lethal,” explained Schneider, who has studied the effects
of mercury on the mata mata turtle (Chelus
fimbriatus). “Because mercury is a persistent substance, it can build up,
or bioaccumulate, in living organisms, inflicting increasing levels of harm on
higher order species such as predatory turtles, fish and mammals.”
Gold mining is on the rise in
many parts of the Amazon basin. And because the mercury used to extract gold
gets into the river system, and then the broader food chain, its effects are
felt far beyond the limits of the mines themselves. In southeast Peru, for
example, the threat mercury poses to environmental and human health has reached
such critical levels that a state of emergency has been declared. It is
likewise a serious problem in Brazil and for turtles in the Amazon Basin.
For turtles, “[t]he biggest issue
at the present is the fact that there are no mercury guidelines specific for
any reptile,” Schneider said. “There is an urgent need to develop and employ
appropriate guidelines for the assessment of Hg toxicity in reptiles, including
turtles.”
Schneider’s study included the
development of “a non-invasive methodology that enables analysis of Hg in
turtles and alligators by using samples from their carapace and skin rather
than killing animals to collect muscle samples.” Results showed that levels of
mercury in the mata mata turtle were high enough to be a health risk for people
eating the animals.
The long-term outlook for the
Amazon Basin’s turtle species will depend on the effectiveness of a
multi-faceted approach to the many threats facing them today. There have
already been numerous calls to halt hydropower development in the Amazon in
favor of greener options, and for better environmental planning to be put in
place for all future infrastructure development. How climate change —
especially increased drought — will impact Amazon turtles remains to be seen.
But when it comes to one of the biggest problems, combatting overexploitation
and trafficking, Lacava sees enforcement as paramount. “I believe that the
illegal trade can only be reduced by police supervision and sustainable use
initiatives,” he concluded.
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