A massive study of nearly 1800 tropical coral reefs around the world has found that marine reserves near heavily populated areas fail to protect many endangered species - but are a vast improvement over having no protection.

The study titled “Gravity of human impacts mediates coral reef conservation gains" appears online this week in the journal Proceedings of the National Academy of Sciences.

A team of 37 scientists collated field studies of fish on a global basis to examine the effectiveness of different reef conservation strategies and the consequences for key species. “Marine reserves near high human pressure had only a quarter the fish of reefs far from human pressures and were a hundred times less likely to have top predators such as sharks,” said lead author Professor Josh Cinner of the ARC Centre of Excellence for Coral Reef Studies.

The study took advantage of a recent trend among coral reef scientists in examining the last remaining wilderness reefs to see how their ecology differed with protection offered by legally established marine reserves near human populations.

Dr. Tim McClanahan, Senior Scientist at WCS (Wildlife Conservation Society) and one of the study’s authors, said: “This represents a monumental effort to study the last wild reef places and to see what people can do to replicate wilderness. The findings are sobering in that even the best reserves are not capable of simulating wilderness. Where human pressure was high, the probability of encountering a top predator was close to zero.”

Human pressure appears to impact reserves even if there is no fishing within the boundaries.  The study finds that the closer you get to human populations and markets, the greater the impacts. Researchers evaluated fish biomass and the presence of top predators on coral reef sites across 41 countries, states, and territories. They used a new way of measuring the human pressures that included fishing and pollution known as the ‘human gravity’ scale.

Human gravity calculates factors such as human population size, distance to reefs, and transport infrastructure on land, which can determine reefs’ accessibility to fishermen and markets.

Professor Cinner added: “A really novel and exciting result arising from using the gravity metric is that medium to high human pressure had the greatest difference between fish biomass in marine reserves and reefs open to fishing. This means that, for most fisheries species, marine reserves have the biggest bang where human pressures are medium to high.”

This work was supported by the John D. and Catherine T. MacArthur Foundation.

The John D. and Catherine T. MacArthur Foundation supports creative people, effective institutions, and influential networks building a more just, verdant, and peaceful world. MacArthur is placing a few big bets that truly significant progress is possible on some of the world’s most pressing social challenges, including over-incarceration, global climate change, nuclear risk, and significantly increasing capital for the social sector. In addition to the MacArthur Fellows Program, the Foundation continues its historic commitments to the role of journalism in a responsible and responsive democracy; the strength and vitality of our headquarters city, Chicago; and generating new knowledge about critical issues.

2018 has been designated by the International Coral Reef Initiative as the third International Year of the Reef. This is a great opportunity to come together to strengthen awareness on the plight of coral reefs, to step up and initiate conservation efforts.