Research Spotlight: Finding bright spots of hope for Caribbean coral reefs

Coral reefs are among the most biodiverse and productive ecosystems on the planet. They are home to an incredible variety of marine life, including many beautiful and brightly colored fish, corals and other organisms, making them popular destinations for snorkelers and SCUBA divers. But coral reefs are not just a pretty place for tourists to visit. These ecosystems provide many other benefits to people and coastal communities. The structure of reefs provides habitats to many species that are harvested for seafood. This structure also provides natural protection to the coastline by dampening wave action and storm surge. The rich biodiversity on reefs has yielded natural compounds that are useful for pharmaceutical and cosmetic products, with many new chemicals yet to be discovered. Coral reefs and their beauty also have aesthetic and cultural values that are difficult to quantify, but are critically important nonetheless to coastal communities.

Despite their importance, coral reefs are an extremely threatened ecosystem. The foundation species of coral reefs – the species that provide the habitat that supports the entire ecosystem – are hard corals. This diverse group of animals builds calcified skeletons that create the reef structure. Without live hard corals, the reef structure will erode over time. Coral reefs around the world are losing hard corals at alarming rates because of direct and indirect impacts from climate change, overfishing, pollution, and coastal development. As these impacts intensify, coral reefs of the future will likely continue to lose their hard coral structure, resulting in reefs that look dramatically different from the coral reefs of the past. Does this mean doom and gloom for coral reefs?

Image captured by Alexandra Dubel.

Many coral reef scholars and conservation practitioners have assumed that reefs with less hard coral provide fewer ecosystem benefits. Some of my recent research, published in the journal Global Change Biology, sought to test this assumption in order to better predict and understand reefs of the future. Do reefs with less hard coral provide fewer or different benefits? My colleagues and I focused on the Caribbean to address this question, where reefs historically had 50-60% live hard coral cover, and now many of those same reefs have 10-20% live hard coral cover or even less. We used a coral reef monitoring dataset, the Atlantic and Gulf Rapid Reef Assessment (AGRRA), which is a collaborative program that compiles standardized data on the condition of hard corals, fishes, and algae at reefs throughout the Caribbean. We assessed 328 reef sites that varied in their amount of hard coral cover. We examined 10 key indicators of ecosystem benefits – including fishery value, coral and fish diversity, coral replenishment, and density of large fish – and evaluated whether those benefits are more likely to be high at reef sites that have higher hard coral cover.

Our results provide a glimmer of hope in an otherwise dismal outlook for coral reef ecosystems. We find numerous ‘bright spots’ at low coral cover sites, a term we use to indicate sites where at least one of the 10 ecosystem indicators is particularly high. In particular, bright spots for the density of large fishes, fishery value, and fish species richness were just as likely to be found at low-coral as at high-coral sites. Large fish and high fish diversity make a site more attractive to SCUBA divers, so this result is good news for the tourist industry. Fishery value measures the market value of the fish at a site if they were harvested and sold for consumption. This indicator is important for the food security and economic prosperity of coastal communities that depend on reef fisheries for their food and livelihood.

Our results do not suggest that we should abandon the “coral” in coral reefs. Some benefits were tightly linked to coral cover, thus ongoing efforts to protect and restore coral reefs are vitally important. But they do indicate that reefs that have lost much of their hard coral cover should not be universally viewed as completely degraded. They can still provide important benefits to people. Other organisms – like soft corals and sponges – may be playing a bigger ecosystem role at low coral sites to compensate for the lack of hard corals. For many reefs, no amount of heroic conservation or restoration effort will be able to fully turn back the clock, so it is imperative that we  better understand and learn how to manage coral reefs with low hard coral cover.

This is not just a question we are grappling with for coral reefs. Human activities are impacting and transforming natural ecosystems the world over. Habitat destruction and degradation, introduction of invasive species, and climate change, among other threats, have caused major changes in the abundance of species and even in what species are found in these altered ecosystems. For example, previously logged forests allowed to recover may be dominated by stands of non-native trees, and many grassland systems are replaced by forest cover because of human alteration of fire regimes. Not surprisingly, these novel ecosystems function differently than they did in the past and may not provide the same suite of benefits to people. The type of approach we used in this research – where we looked at the range of outcomes for ecosystem benefits to search for “bright spots” – is applicable to any type of ecosystem and will help us better manage the altered ecosystems of the Anthropocene.

Dr. Lester is an assistant professor in the Department of Geography at Florida State University. You can find out more about their research at their website.

The feature image is from Sarah Lester.

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