Coral reefs provide the foundation for the livelihoods of people living on island nations. Photo credit: Ishan
Despite the threats that reefs face, scientists believe there may be hope for recovery of these ecosystems.
As you may have read in the first part of this article, the destruction of reefs is multifaceted: threats like ocean acidification, pollution, disease, and increased temperature work together not only destroy reefs but also prohibit them from adapting to new conditions.
It is often difficult for coral reef scientists to maintain optimism in the face of such rapid change; saving coral reefs presents one of the most urgent challenges that science faces today. If we are going to combat these large-scale factors, we will need a combination of technology, policy, and a little help from the ecosystems themselves. Let’s talk about what that looks like.
Maybe the greatest chance that corals have at surviving long into the future is not in our hands, but in their own. Natural selection guides evolution by encouraging diversity: in every destructive event that coral reefs face, some corals will survive over others. Some will be more disease resistant, and will survive an outbreak to pass on these genes to their offspring. Some will have genes that improve calcification, and as ocean acidification sweeps the reef, these corals will continue to grow despite the acidic conditions.
Bleaching on a reef is a spectrum: some are more resistant than others. Photo credit: Mia Hoogenboom
The differences in traits in corals of the same species are what allow that species to endure into the future. The same goes for lizards, rabbits, bacteria and us: genetic diversity is the key to staying alive. Some corals grow faster than others, some secrete more protective mucus, some possess pigments that glow vivid colors under UV light and act as a special sunscreen.
Every time a mass bleaching event has impacted a reef, we find corals that are capable of withstanding it. These corals are more resilient, and are better suited to warmer, more acidic, and more variable ocean conditions. This is awesome news. Adaptation to these new conditions can happen, and reefs can become more adjusted in the long term.
However, the rate of evolution is slow. The increases in temperatures in the ocean are moving too fast for corals to adapt, and although some might survive for a while, we cannot expect corals to evolve fast enough to outpace the onslaught of climate change. While scientists now recognize that the initial predictions of complete coral reef destruction in the next 30 years or so likely exaggerate the decline, we have indeed reached a threshold where coral reefs are unlikely to recover without our intervention. Here’s where we come in.
In this lab, corals are subjected to stressors to make them more resilient. Photo credit: NOAA
What if we could assist the evolution of corals to be more tolerant of new conditions? What if we could find corals with those specific traits that would allow them to survive and breed those over and over again to create stronger populations? What if we could engineer those traits and create new and improved coral reefs?
It turns out, we can do these things, and we are doing them now. Artificial engineering isn’t a new science; we’ve been doing it for thousands of years. We identified traits we liked, and through artificial selection, we created organisms that bore as little resemblance to each other as a Rottweiler and a Shih Tzu.
In coral reef nurseries and laboratories, scientists are mixing old ideas with new techniques to assist the evolution of coral reefs and hopefully assist their survival in a changing world.
There are multiple ways to do this. One technique currently being used is exposing adult corals in the lab to stressors such as high temperature or low pH; this stress induces changes in the genes of the coral through epigenetic shifts that make it more prepared to handle the next stress event, almost like developing a resistance. These epigenetic shifts actually alter the DNA, and this coral will be able to pass these genes to its offspring, leading to more stress-tolerant descendants.
The Coral Restoration Foundation (CRF) in the Florida Keys grows coral fragments in nurseries, then plants them back out on the reef. Photo credit: Pol Bosch
Another technique works by manipulating the bacteria associated with each coral (of which there are many) with the goal of finding a partnership between coral and bacteria that is more resistant to stress. One method currently being explored even involves engineering heat-tolerant zooxanthellae that would be resistant to bleaching. Finally, actual selective breeding of corals through coral “gardening” is being used in nurseries all over the globe to select for and grow corals with desired traits.
The use of all these tactics has resulted in success; we are indeed able to assist the evolution of more adapted corals.
When thinking about coral restoration, some scientists in recent years have come to the conclusion that assisting the evolution of coral will not bring back reefs on its own; we must focus on repairing the ecosystem as a whole. This ‘top-down ecological approach’ focuses instead on rebuilding populations of keystone species that serve a specific function on the reef, such as reintroducing long-spined sea urchins in the Caribbean to graze the algae off reefs and make room for coral larvae to settle, or making certain predatory fish species (such as grouper) protected by law so they can continue to control smaller fish populations.
Whole ecosystem approaches recognize the fact that the health of an environment is partially dependent on all of its components, and if we can reestablish the ecosystem services that allowed corals to thrive, we can preserve the life of reefs in the long term. Recovering larger populations of coral and coral-associated animals in the next few years would also allow for faster adaptation of the entire ecosystem to changing oceanic conditions (higher numbers mean higher diversity, and diversity is the key to speeding up evolution!). This gives us hope. But coral reefs cover a significant portion of the ocean’s area, and science alone will not be able to scale up these efforts enough.
For this, politics comes into play.
Parrotfish graze on the algae on reefs, allowing corals to grow without competing for space. Photo credit: Caradonna Adventures
The establishment of Marine Protected Areas (MPAs), no-take zones (NTZs), and strictly-managed marine fisheries have allowed for degraded reefs to recover to healthy levels at astonishingly fast speeds. Although it is changing, the ocean itself is extremely resilient and capable of minimizing stress, and when given the opportunity, reefs do heal. Expanding these protected areas, passing more laws restricting catch numbers and protecting keystone species will ensure that ecosystems can rebuild, and our fishing practices can remain sustainable.
Pollution, as a key driver of climate change, poses the biggest threat to our oceans. Photo credit: Sam Jotham Sutherson
Ensuring the survival of coral reefs will also require that we reduce global carbon dioxide emissions. While it is unrealistic to expect nations to immediately scale down the use of fossil fuels as an energy source, it is imperative that we invest in developing the framework for reducing the cost of renewable energy.
If we can bring down the cost of no-emission energy sources such as solar, wind and hydroelectric power, as well as improve the technology required for electric vehicles, we will be able to successfully transition to lower emission states, and the planet’s built in systems of bioremediation can begin to repair the environment. While this will not stop the input of greenhouse gases into the atmosphere, it will slow down the process, allowing corals and other such environments to adapt.
Even with our efforts in ecosystem engineering and assisted evolution, what coral reefs truly need right now is time; if we can slow down the progression of climate change, improve our fishing practices and cut down on pollution, they may be able to recover on their own.
All of this in mind, it is important to recognize that the focus of coral restoration efforts should not be returning these ecosystems to the condition that we observed them in before they started dying off; considering how much the earth continues to change, this mindset would not be practical or effective. The world’s environments are changing: this is a product of human progress, and accepting that we will continue to advance technologically in the future assumes that the world around us will continue to change as well. It is our responsibility, however, to make sure our impact on the climate and our ecosystems is not so destructive. As our technology improves, we will actually be granted the opportunity to remedy some of this damage.
Renewable energies, sustainable agricultural and fishing practices, and genetic engineering will allow us to progress productively into the future without destroying ecosystems that have provided these services to us in the past. For now, the general positive characteristics of coral reefs, such as high levels of coral cover, fish biomass, biodiversity and 3D reef structure should be used as goals that we can build towards. Scientists have identified several characteristics that will be important in future reefs, including tolerance to warmer and more acidic waters, resistance to disease, tolerance to fluctuations in nutrients and salinity, and higher skeletal densities, to name a few. Hopefully, the reefs in 50 years will reflect these changes.
Recovery of coral reefs will not happen overnight; it will happen over tens or maybe hundreds of years. But with a little regulation, a little science and a lot of investment in new technologies, I believe it can happen.
- Jason
A fish hides in the branches of an Acropora coral, which it depends on to stay alive. Photo credit: Tomoe Steineck