Study Warns of 70% Biodiversity Loss in Caribbean Coral Reefs

Boston, Massachusetts — Human activity has reduced the trophic complexity of Caribbean coral reefs by up to 70%, according to an international study published in Nature and led by Jessica Lueders-Dumont of Boston College.

The research team found that food chain length decreased by 60% to 70%, while the functional diversity of fish declined by 20% to 70%. This simplification process has reduced ecological resilience and endangered both marine diversity and the food security of millions of people.

Coral reefs host at least 25% of marine species and provide coastal protection and food for approximately 1 billion people, according to Boston College data. In the Caribbean, these ecosystems have lost more than 50% of their coral cover since the 1970s, compromising their productivity and ecosystem services.

The study used nitrogen isotope analysis of otolith fossils and coral fragments from Panama (Bocas del Toro) and the Dominican Republic (Enriquillo Basin), covering a period of 7,000 years. This method allowed researchers to compare food chain structure before and after human impact.

The team analyzed 136 fish otoliths and various coral samples to assess trophic range and dietary specialization. According to co-author Xingchen Wang of Boston College, this approach enabled direct reconstruction of ancient food webs.

Results show that in ancient reefs, fish communities consumed a greater variety of resources, promoting ecosystem stability and resilience. Lueders-Dumont explained, “In healthier Caribbean reefs, fish communities fed on a greater variety of resources.” In contrast, contemporary reefs show homogeneous diets, with multiple species relying on the same food sources and limiting adaptive capacity.

The study documented significant contraction of trophic complexity: both in Panama and the Dominican Republic, food chain length fell by approximately 60% and fish functional diversity decreased by 20% to 70%, depending on region and group.

The Dominican Republic showed more marked simplification, attributed to greater overfishing pressure, loss of coastal habitats, and pollution. Fish such as gobies (at the lowest trophic level), as well as grunts and cardinalfishes (at intermediate and higher levels), experienced reductions in both diet diversity and trophic position.

The detected homogenization and shortening of food chains pose immediate risks to reef ecological resilience. The article warns that dietary convergence and reduced specialization increase ecosystem vulnerability to sudden changes.

When resource diversity disappears, the entire fish community faces similar pressures, limiting its response and recovery capacity to disturbances. The authors maintain that loss of functional diversity raises the probability of collapse in current reefs.

The team linked this simplification primarily to human activities such as rising global temperatures, overfishing, excess nutrients from agriculture, and coral habitat deterioration. Additionally, loss of mangroves, decreased habitat connectivity, and reduction of top predators altered energy flow, affecting the entire food web.

The paleoecological reconstruction developed in the research not only documented loss of complexity in coral reefs but also established an ecological baseline before human impact, essential for defining marine conservation and restoration goals. “We can now glimpse what pristine coral ecosystems were really like and how we might restore them,” concluded Lueders-Dumont.

The study’s findings indicate that modern coral reefs operate with fewer trophic pathways and present less functional redundancy than in the past, limiting their resistance to new pressures and increasing the risk of future ecosystem collapse.