By Siri Grund

International Day for the Conservation of the Mangrove Ecosystem, marked annually on 26 July, offers a timely reminder to discuss the benefits these ecosystems provide and how they have been impacted due to climate change.

This day was adopted by the General Conference of the UN Educational, Scientific and Cultural Organization (UNESCO) in 2015. Activities marking this day seek to “raise awareness of the importance of mangrove ecosystems as ‘a unique, special and vulnerable ecosystem’ and to promote solutions for their sustainable management, conservation and uses.”

A review of research presented during the fourth Mangroves and Macrobenthos Meeting, which took place the year after the International Day was established, on how mangroves have been affected by climate change offers some suggestions on how to counter those impacts. With this year’s celebration of the Day accompanied by forest fires, floods, and rising temperatures around the world, it is worth reflecting on the interlinkages between climate change and mangrove ecosystems.

Mangroves are located in “transitional intertidal zones.” This means these ecosystems are at the intersection of SDGs 14 and 15 as they provide a buffer zone between life below water and life on land. Mangrove trees are easily identifiable because their roots are visible at the water’s surface. They provide regulating ecosystem services such as sediment trapping, coastal defense, and carbon storage as well as provisional ecosystem services such as timber, fuelwood, and fisheries. Mangroves are found in the tropics and sub-tropics on coastlines, but anthropogenic changes and climate change are changing the landscape that mangroves inhabit.

Ever since the middle of the 20th century, mangrove deforestation has caused a substantial loss of mangrove ecosystems. According to the UN Environment Programme (UNEP), aquaculture is the leading cause of anthropogenic loss, while overexploitation, pollution, and coastal development also contribute.

Increasing extreme weather events, rising sea levels, and other impacts from climate change have contributed to mangrove losses. Mangroves need to be above the water’s surface to survive. Many mangroves are unable to adapt fast enough to the rate of rising sea levels, so they are effectively washed away. Extreme weather events such as long droughts and freezing temperatures can also lead to mangrove loss. 

In addition to the loss of mangrove ecosystems in some areas, climate change has increased the presence of mangroves in new areas. The combination of warmer winters and rising sea levels has pushed mangroves into ecosystems that have historically been occupied by saltmarsh plants. For example, the increasing presence of mangroves along the northern coast of Florida illustrates the changes that can be attributed to warming temperatures. In the past, these areas did not provide the conditions that would allow mangroves to survive. These new areas of mangroves are replacing areas formerly occupied by saltmarsh plants, although they are not perfectly adapted to these new conditions. Extreme weather events such as hurricanes or extended freezing periods kill these mangroves.

The impacts of this transition from saltmarsh plants to mangrove trees are still unknown. The presence of mangroves is predicted to lead to an increase in carbon sequestration, but the ecosystem and provisional services that saltmarshes provide will be disrupted.

Given the changing locations of mangroves, researchers have been studying the possibilities for mangrove rehabilitation and regeneration and the conditions that are most suitable for their growth. Remote sensing technology can provide an idea of where mangroves are undergoing stress so that losses can be prevented. Regeneration has been successful in Florida and Indonesia, but not when planting mangroves was the primary concern. Instead of focusing on planting as many mangroves as possible, these successful mangrove restorations occurred as a result of following the Principles of Ecological Mangrove Rehabilitation. These principles challenge communities to consider the social, economic, and ecological factors prior to beginning rehabilitation.

International Day for the Conservation of the Mangrove Ecosystem provides an opportunity to research and celebrate this unique ecosystem. The research on mangroves shows they provide ecosystem services that benefit life on land (SDG 15) and life below water (SDG 14), but they are very vulnerable to climate change (SDG 13). These ecological interlinkages, as well as social and economic factors, must be kept in mind when considering rehabilitation projects.  

This article was authored by Siri Grund, IISD Generation 2030 intern. She is majoring in environmental studies and health equity and health promotion at the University of Wisconsin, Madison.