This article is part of the 4sea project.
“A healthy planet is essential for a peaceful future …Every year, more than 8 million tons of plastic end-up in the oceans.”
M. Guterres, UN Secretary-General,World Environmental Day on June 5th, 2018.
Recognized as one of the greatest universal challenges by the international community , this year plastic pollution has been the central focus of the Earth Day (April 22nd), the World Environmental Day (June 5th) and the International Ocean Day (June 8th), with the objectives of raising awareness on this issue and engaging communities at all levels to fight against plastic waste, especially in the oceans.
A “healthy ocean” according to Mr. Thomson, UN Secretary General’s Special Envoy for the Ocean, is “vital to the achievement of sustainable development”. However, today, more than ever, the oceans are facing challenges that made them a threat for marine environment and human life.
To naturally face these challenges, coral reefs have always played a strategic role, especially on protecting coastal communities, harbouring what is considered the highest biological diversity of any ecosystem on the planet, and providing food and income for more than 850 million people who live within 100 km of reefs . Today, because of climate change and plastic pollution, this role of protection is threatened.
Coral reefs: a natural bulwark against risks for coastal communities impacted by climate change
Healthy coral reefs are a natural bulwark protecting coastal communities against ocean risks caused by climate change. Healthy coral reefs act as natural barriers and protect simultaneously the ecosystems located between the reefs and the coasts and the human settlements located on coastal zones against the elements from the offshore waters. They contribute to reduce the intensity and damages associated to storms, hurricanes, cyclones and, to a certain extent, the energy of tsunamis. Healthy coral reefs also contribute to reduce the coastal erosion by absorbing the energy from the waves, which by their repeated actions, dig the beaches and the undercutting of the cliffs and move the sediments through the offshore waters. Today, the oceans cover 71% of the Earth’s surface. Coral reefs represent 0.2% of the oceans and protect around 272 million people who live in the direct vicinity of coral reefs (within 30 km of reefs and less than 10 km from the coast)  on the 150 000 kilometers of coastline in more than 100 countries and territories .
The ocean is one of the lungs of the planet. It absorbs CO2 from the atmosphere and provides most of the oxygen we breathe. However, this natural role of carbon sink is now under pressure. According to the World Meteorological Organization (WMO) Statement on the State of the Global Climate in 2017  released in March 2018, today the oceans absorb 30% of CO2 anthropogenic emissions. This high level of CO2 absorbed modifies the pH of seawater and causes ocean acidity to increase, which has some effects on marine ecosystems and especially on the health of the corals.
Moreover, according to the Institute of Atmospheric Physics of the Chinese Academy of Sciences, 2017 has been the “warmest year recorded in the oceans”. Corals are sensitive to water temperature. Their life is only possible on a small range of temperature. The current upward trend of the ocean temperature (in surface and deeper) causes the bleaching of coral reefs, which can lead to death when corals are exposed to warm water for a long period of time.
The impact of rising ocean temperatures and the other stressors related to climate change on coral reefs could affect their role in protecting coastal communities .
Plastic pollution: an additional stress for coral reefs
Every year, more than 8 million tons of plastic waste  enters in the ocean. The effects of the plastic pollution in the ocean overlap the ones caused by climate change and play a role of threat multiplier. Among these plastic waste impacts in the ocean: the serious damages caused on coral reefs and its consequences on marine ecosystems, coastal communities and human well-being.
Plastic waste causes irreversible damages on corals, as it has been recently outlined in Plastic waste associated with disease on coral reefs, a scientific report led by Joleah B. Lamb from Cornell University and based on an observation of 124 000 corals in 159 coral reefs in Asia-Pacific Region and in particular in Myanmar, Thailand, Indonesia and Australia. 
The Asia-Pacific Region contains 55.5% of global coral reefs  and encompasses 73.0% of the global human population residing within 50 km of a coast , which depends to most on coral reefs for coastal protection and fisheries . This region is already the most exposed to the effects of ocean warming and acidification on corals and could be more affected due to plastic pollution. Indeed, today 11.1 billion plastic items are entangled on coral reefs in this region. By 2025, according to the estimates made by Joleah B. Lamb & al, the amount of plastic items should reach 15.7 billion .
During the observation phase, Joleah B. Lamb & al have analysed the effects of plastic waste on corals and have noted that plastic waste multiplies by twenty the risks for corals to develop irreversible diseases . In fact, plastic waste attacks directly the coral tissues, which are not able to be restored and thus threatening directly the future of coral reefs and indirectly the future of coastal communities.
According to Serges Planes, Director of the CRIOBE – Centre for Island Research and Environmental Observatory and expert on coral reefs, “the coral is the core element of a coral reef”. If corals come to disappear by the conjunction of plastic pollution and global warming, coral reefs won’t be able to provide services to coastal communities anymore.
Integrated approach: the solution to tackle coral reefs’ challenges
In the last forty years, 40% of coral reefs have already disappeared . According to experts, 90% of coral reefs will be under danger by 2030 and nearly all reefs will be threatened by 2050 . Today, more ambitious and integrated actions are needed to avoid the global decline of coral reefs.
To better take a stock on the coral reefs situation and envision the future, 2018 has been stated, for the third time, as the International Year Of the Reef. Today more research is focusing on actions to mitigate climate change, protect and repair ecosystems, and adapt coastal communities to the impacts of climate change on coral reefs, which gives a better understanding of the options available for action .
The 2030 Development Agenda offers a unique opportunity to develop a multi-sectorial, multi-level, and multi-actors approach to tackle all the challenges related to climate change and plastic pollution at the same time. Coral reefs are the perfect illustration of the importance of an integrated approach.
At the United Nations Climate Talks in Bonn, Germany in May 2018, a focus has been made on adaptation and loss and damage for vulnerable communities living in coastal areas. Finding the way to strengthen the resilience of human settlements facing climate shocks won’t be efficient if we don’t find sustainable solutions to tackle plastic pollution at the same time.
About the author: Sabrina Marquant is a former YOUNGO Focal Point and a member of the CliMates advisory committee. She is also a climate diplomacy expert who has participated on the elaboration of the Paris Agreement. Right after the COP21, she had been involved in some international initiatives and projects to step up climate ambition. She is now developing an expertise on climate risks and resilience. She recently launched EcoWaves Connection, a project which envisions to build resilience and empower coastal areas’ local communities to better face climate change impacts.
This article has been written in the context of 4sea. 4sea, a project about the importance of the world oceans, addresses the interdependence between the oceans and climate change, entraining everyone to become ocean lovers. 4sea is a joint project between the youth organisations CliMates, Youth for Ocean and Vitamin Sea. Love it? Stay tuned for more!