The Barrier Reef shared by Belize, Guatemala, Honduras and Mexico, the second longest in the world, is being severely damaged by human activities. More than 80 percent of the sediment and 50 percent of the pollutants entering the coastal waters of the Barrier Reef originate from human activities in nearby mountainous Honduras, according to the World Resources Institute (WRI).

The analysis is the first to determine the origin and volume of sediment and pollution that run off agricultural lands, via the region’s vast river networks, into the neighboring Gulf of Honduras and Caribbean Sea.

“As humans have altered the landscape, an increasing amount of sediment and nutrients are reaching coastal waters and the Mesoamerican Barrier Reef itself,” said Lauretta Burke, a senior coastal ecosystem expert at WRI and co-author of the study. “Our analysis shows that pollution from farms in Honduras can inadvertently damage the entire Mesoamerican reef, which provides an important source of revenue from tourism and fisheries.”

Along with more than 80 percent of sediment, more than half of all nutrients (both nitrogen and phosphorous) originate in Honduras.

Guatemala was identified as a source of about one-sixth of all sediments and about one-quarter of all nitrogen and phosphorous entering coastal waters along the reef.

Compared to the other countries, relatively minor percentages of the regional sediment load come from Belize and the Yucatan Peninsula in Mexico. Belize contributes between 10 to 15 percent of nutrients and Mexico is estimated to contribute about 5 percent of the nutrients from all modeled watersheds.

Of the 400 watersheds in the region, the Ulua watershed in Honduras was found to be the largest contributor of sediment, nitrogen, and phosphorous. Other large rivers found to be significant contributors of sediment and nutrients are the Patuca (in Honduras), Motagua (in Guatemala and Honduras), Aguan (in Honduras), Dulce (in Guatemala), Belize (in Belize), and Tinto o Negro (in Honduras).

Under land-use scenarios which favour free markets and little policy regarding the environment, nutrient delivery is likely to increase by about 10 percent by 2025, while sediment delivery might increase by 13 percent or more.

If environmental policies that favour sustainable development are implemented, nutrient and sediment delivery are likely to be reduced by at least 5% from current levels, promoting recovery of degraded corals.

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