When the 6.2 magnitude earthquake struck just over two weeks ago, at least 23 people were killed, most in landslides. Humans, however, were not the only victims.
Thousands of fish in the SarapiquíRiver were killed when mudslides choked the waterway, turning it into a continuous trough of sludge. Researchers fear that the river’s entire fish population may have been wiped out.
“For the Rio Sarapiquí, the earthquake was a catastrophe,” said Ron Coleman, a researcher from SacramentoStateUniversity in California. “As far as we can tell, the mud that went into the river choked all the oxygen out of the water and killed all of the fish and likely much of the other aquatic life.”
While the full picture of damage to infrastructure, homes and citizens in the area hit hardest by the Jan. 8 quake is now beginning to come into focus, the full scope of environmental damage remains unclear.
The Environment, Energy and Telecom munications Ministry (MINAET) estimated that 550 square kilometers (about 212 square miles) were adversely affected in some way by the earthquake.
Rafael Gutiérrez, the director of the Cordillera Volcánica Central Conservation Area, the MINAET office that oversees protected lands in the quake area, confirmed Coleman’s report on the SarapiquíRiver.
“The landslides have caused the accumulation of mud that … blocked oxygen, and the fish have died in extremely large quantities,” Gutiérrez said. “We have reports (of dead fish) from the area of Cariblanco, the mouth of the San Juan River and including Barra de Colorado.”
Coleman, who has been researching freshwater fish in the region for 14 years, was in the Caribbean plains the day of the earthquake, based at the La Selva Biological Station, and arrived at the banks of the SarapiquiRiver the following day.
“Workers at La Selva, who live in that area, said that local people were at the river right after the quake and well into the night collecting dead fish. We understand that there were dead fish by the thousands,” Coleman said. “When we went, even though most had been picked up, we still found dead fish. These included all life stages from very young fish to breeding-sized adults.” It appears that none survived the event.”
Locals told Coleman that “the water actually appeared to cease flowing downstream” because of the thickness of the mud in the river.
“When we went the next day, the water was moving again but you could see a thick coat of mud (about 4 inches) covering everything,” Coleman wrote. “Even in the main channel we could see that the clearer water was flowing over top of a much thicker layer of water and mud below it.”
The researcher said the short-term damage to the river ecosystem is severe. He and other scientists believe that not only are all the fish gone, but also the small organisms they feed on. Birds like the kingfishers and creatures that feed on fish will have to go elsewhere in search of food, he said.
“Crocodiles, otters and other larger animals will also likely move out of the main river,” Coleman added.
“The good news is that in the days following the quake, we looked at the Río Puerto Viejo and the Río Sardinal, two important tributaries of the Sarapiquí, and they both look perfectly fine,” Coleman added. “In fact, we found breeding fish in both rivers days after the quake. Over time, fishes and other creatures from these rivers will move into the Sarapiquí.”
As for damage to terrestrial animals and ecosystems, MINAET has convened several teams to investigate. An initial report on the damage to forests and soil is due next week.
“What happened to the forest? In what way can we intervene? These answers are not yet defined, but we are looking at our alternatives,” Gutiérrez said. “One is to let nature recuperate on its own, and this implies expanding the protected areas inside the region.”
MINAET is also going to work with the University of Costa Rica, the NationalUniversity and the National Biodiversity Institute in evaluating the impact on wild animals in the area.
Coleman cautioned against any attempts at a quick fix for the affected ecosystems, such as trying to stock the SarapiquiRiver with fish.
Estimating that recovery could take “several years, at least,” Coleman called for patience, and faith in nature.
“It will take time for the many processes that need to occur to happen, for example the mud needs to flush out of the system, the small bottom creatures need to recolonize and the fishes need to move back in,” he said. “Ecology is very complex and countless examples from other systems have shown that when we try to mess with it, we make things worse.”
There is good news, however. “The tributaries are in good shape and will rebuild the Sarapiqui system,” he said.