Mangrove decline through the ages in Central and South America

STRI/DICYT As deforestation erases the thin, green line of mangrove forests along tropical shores, a new study looks to the past to provide conservation lessons for this essential ecosystem. Scientists from Colombia’s Talking Oceans Foundation, the University of York, U.K., and the Smithsonian in Panama document mangrove use and decline through the ages along the Pacific coastline of Costa Rica, Panama, Colombia and Ecuador.

Since the colonial era, particularly in the 20th century, deforestation for timber, shrimp aquaculture or beachfront development has vastly reduced mangrove forest cover in the region. The new study, published in Forest Ecology and Management, creates a baseline for remaining forest area in the region, which can inform regional initiatives to protect this vital, shared ecosystem.

“Mangroves are nurseries for important food fish species, including six species of snook, seven species of snappers, over twenty species of corvinas, and numerous catfish,” says coauthor Richard Cooke, senior staff scientist at the Smithsonian Tropical Research Institute. Archeological and ethnological evidence suggests that there was an ancient and robust pre-Columbian trade in Pacific estuarine fishes, which were likely mass-captured, salted, dried in the sun and transported as far as 13 to 60 kilometers inland. Archeologists can infer this by comparing fish species composition and other cultural data in ancient kitchen trash heaps with data on modern fish trapping and preparation methods, Cooke explains.

“Mangroves also form important barriers against storm surges and floods, and huge drainage channels that prevent silting, flooding and malodorous waters when the sewage system fails,” he adds. These ecosystem services have long been overlooked.

Lead author Juliana López-Angarita, PhD student at University of York, says that attitudes toward mangrove forests changed since the 1990s as people learned more about their importance. “We were able to highlight important successes and failures of national policies and protection schemes in the four countries, to guide future policy that strengthens mangrove conservation and associated livelihoods,” she says.

The study suggests that since monitoring began, Panama has lost the greatest amount of its mangroves (about 68 percent), followed by Ecuador and Colombia. Costa Rica, despite having the smallest mangrove area (39,000 hectares), still has the largest area of intact mangroves under protection, around 59 percent. Panama protects about 43 percent of roughly 154,000 hectares of mangrove forest. Colombia protects less than 24 percent of its 214,000 hectares.

The researchers found that although mangrove management plans vary regionally from absolute no-take policies to mixed-use and limited take arrangements, policy does not always translate to on-the-ground oversight and protection. Challenges to protection include limited personnel or financial resources, political will, as well as illegal harvesting or wetland buyout by private entities.

The four countries in the study region are part of the Eastern Tropical Pacific Marine Corridor (CMAR Pacífico) conservation initiative, which aims to improve resource management across the ecoregion, and disseminates information to government bodies, nonprofits and educational institutes.

“Nowadays, knowledge of mangroves’ importance is widespread not only among government representative but also in local community groups that self-mobilize to protect mangroves against land developers,” said López-Angarita. “Our study comes at an opportune time for an international agreement aimed specifically at the protection of mangroves in the Eastern Tropical Pacific.”

López-Angarita, J. et al. Mangroves and people: Lessons from a history of use and abuse in four Latin American countries. Forest Ecology and Management 368:151–162. DOI: 10.1016/j.foreco.2016.03.020