Over the next 30 years, mangrove forests face the threat of disappearing off the face of the Earth due to climate change—particularly rising sea levels—a new study has revealed.
Saviour of coasts: mangroves
Mangroves are said to be highly resilient ecosystems that form at the edge of land and sea as they can withstand excessive salt, and their tangled roots host several aquatic and amphibian life. Mangroves are also a crucial buffer during storms and floods—thus protecting the coastal communities and natural habitats from its severe impacts.
Worldwide, there are about 80 different species of mangrove trees. India consists of the largest mangroves in the world—the Sundarbans. For the environment, mangroves are crucial for carbon-storing, and it is said that they can hold more gas than a rainforest of the same size. Their ability to store blue carbon—carbon captured by the aquatic ecosystems—in high amounts is extremely important to mitigate climate change.
But now, as global warming affects ecosystems worldwide, mangroves too are likely to face the brunt of the rising sea levels in the coming years. In fact, they may end up completely submerging below the seas in a matter of decades, says a study published in the journal Science.
The loss of mangroves ecosystems can have disastrous impacts, the deadliest of which would be an increase in the carbon dioxide concentration in the atmosphere. These forests also soak freshwater from saline seawater, which helps fish, crustaceans, and shellfish to survive. They function as a safe harbour for all beings, protecting about 5.3 million people around the world, along with several coastal animal species, from floods, storm surges, and other effects of sea-level rise.
Rising sea-levels threaten mangroves
According to the IPCC, the sea levels are rising at an average rate of about 3.4 mm per year—in comparison, the rate of rising was about 1.8 mm per year during the 20th century. In fact, due to the rapidly warming globe, this rate is projected to increase up to 5 mm per year over the next few decades, and reach 10 mm per year by 2100! This poses a major threat not just to resilient mangroves, but also most species near the coasts, including humans.
Researchers estimate that mangroves can more or less survive as long as the sea-level rise is limited to 5 mm, i.e. about 0.2 inches per year. But this scenario is only possible if low emission is maintained. If not, and the sea levels rise by say 6 mm per year, mangroves will die out by 2050, the research warns.
To understand the sea-level rise pattern, researchers examined the sediment data of 78 mangrove ecosystems dating back to 10,000 years from across the globe. The collected data revealed the pattern of mangrove growth with respect to the sea-level rise over the past 10,000 years.
"Under high-emissions scenarios, rates of sea-level rise on many tropical coastlines will exceed 7 millimeters per year, the rate at which we concluded there's a 6.2 percent probability mangroves can sustain growth," said co-author of the study Erica Ashe, from Rutgers University. The results concluded that mangrove ecosystems witnessed growth only when the sea-level rise was below 7 millimeters a year. But if their roots are completely submerged for too long, the mangroves will perish.
According to reports, mangroves can bear and balance the sea level rise by building in a vertical direction. However, the increase in flood-like situations due to rising sea-level can cause trees with small breathing roots to die.
Therefore, in order to protect the environment of mangroves forest across the globe, it is vital to reduce the carbon footprint. Not just for the mangroves, but also for the entire biodiversity which thrive on Earth.
