Mangroves—tropical and subtropical ecosystems that cover nearly 150,000 km² across 120 countries—are bearing the brunt of the consequences of human activities, even as they play crucial roles for many human populations and the planet. In this first part, we will detail the unique characteristics of mangroves, their importance to Sri Lanka, and their vulnerability to the impacts of climate change.
Mangroves are unique coastal forests that grow where land and sea meet in tropical and subtropical regions. These ecosystems are made up of salt-tolerant trees and shrubs that survive in muddy, oxygen-poor soils regularly flooded by tides 1¯2. Although mangroves may appear harsh and difficult environments, they are among the most productive ecosystems on Earth and support a wide range of marine and terrestrial life 3. They provide food, income, coastal protection, and environmental stability for millions of people worldwide, especially for fishing communities 4¯5.
Today, mangroves face serious threats from climate change and human activities. Rising sea levels, stronger storms, pollution, deforestation, shrimp farming, and coastal development are causing rapid degradation of mangrove forests around the world 6¯7. As these ecosystems disappear, coastal communities lose important natural protections and economic resources 8. This paper explores the characteristics of mangroves, the main threats they face, the ways they adapt to difficult environmental conditions, and the importance of protecting them through both local and global conservation efforts.
What are mangroves and why are they important?
Globally, mangroves cover around 150,000 square kilometers and are found across Asia, Africa, the Americas, Oceania, and parts of the Middle East 9. Asia contains the largest concentration of mangroves and the highest diversity of species 10. Southeast Asia is considered the global center of mangrove biodiversity, containing around 51 mangrove species 11.
Mangroves provide extremely valuable ecosystem services. One of their most important functions is coastal protection. Their dense roots help stabilize shorelines, reduce erosion, and weaken the force of waves and storm surges during hurricanes, cyclones, and tsunamis 12¯13. This natural barrier helps protect millions of people living in coastal regions 14.
Mangroves are also major carbon sinks. They store enormous quantities of carbon in their soils and vegetation, often much more than tropical forests on land 15¯16. Because of this, mangroves play an important role in reducing climate change by capturing and storing atmospheric carbon dioxide 17.
In addition, mangroves support fisheries and biodiversity. Their root systems create safe nursery habitats for juvenile fish, crabs, shrimp, mollusks, and many other marine species 18. Many fish species important for local and commercial fisheries spend part of their life cycle in mangrove ecosystems 19. Birds, reptiles, mammals, and insects also depend on mangroves for food and shelter 20.
Mangroves also provide economic resources to local populations. Coastal communities use mangrove wood for houses, boats, fences, tools, and fuel 21. Some mangrove species are used in traditional medicine, cosmetics, soaps, and insecticides 22. Millions of people worldwide depend directly or indirectly on mangroves for their livelihoods and food security 23.
Special characteristics and adaptations of mangroves
Mangroves grow in salty wetlands and intertidal zones where conditions are difficult for most plants 24. These environments are characterized by high salinity, muddy soils, extreme tides, strong winds, and low oxygen levels in the soil 25. Despite these conditions, mangroves have evolved special adaptations that allow them to survive and flourish 26.
Salt tolerance
One of the main challenges for mangroves is salt. Many mangrove species grow in areas flooded daily by seawater 27. To survive, they have developed different mechanisms to manage excess salt. Some species filter salt at the root level before it enters the plant (ibid.). Others excrete salt through special glands in their leaves 28. In some cases, salt accumulates in older leaves that later fall off the tree 29. CThese adaptations allow mangroves to survive in salinity levels much higher than most other plants can tolerate 30.
Adaptation to low oxygen soils
Mangroves grow in muddy soils that contain very little oxygen. To solve this problem, they have developed specialized root systems that allow them to breathe above the water surface 31. Species varies in root shapes:
- Stilt roots help stabilize trees in soft sediments 32.
- Pneumatophores are vertical roots that rise above the mud to absorb oxygen from the air 33.
- Knee roots and plank roots also help with oxygen intake and structural support 34.
These root systems not only help the trees survive but also create habitats for fish, crabs, oysters, algae, and many other organisms 35.
Ecotonal nature
Mangroves are considered an ecotone because they form a transition zone between terrestrial and marine ecosystems 36. This position between land and sea makes them biologically rich and highly productive 37. Mangrove ecosystems connect with coral reefs, seagrass beds, lagoons, and rivers. Many marine species move between these habitats during different stages of their lives (Ibid.). Juvenile fish often use mangroves as nurseries before moving to coral reefs or open waters as adults 38. Because of this ecological connectivity, the destruction of mangroves can negatively affect entire coastal ecosystems and fisheries 39.
Climate change and its effects on mangroves
Climate change is becoming one of the greatest threats to mangrove ecosystems. Rising temperatures, sea level rise, changing rainfall patterns, and stronger storms are already affecting mangrove forests around the world 40.
Sea level rise
Sea level rise is particularly dangerous for mangroves because they depend on a delicate balance between land and water 41. If sea levels rise too quickly, mangroves may become permanently submerged 42. Historically, mangroves adapted by slowly migrating inland. However, today many coastlines are occupied by cities, roads, and infrastructures, preventing this natural migration 43. Scientists estimate that a large portion of global mangroves could disappear or become submerged by 2050 if sea levels continue to rise rapidly 44.
Rising temperatures
Temperature strongly influences mangrove growth and distribution 45. Moderate warming may allow mangroves to expand into new regions farther from the equator 46. In some areas, mangroves are already spreading into temperate salt marshes 47. (Saintilan et al., 2014). However, excessive heat can damage mangrove physiology. High temperatures reduce photosynthesis, increase evaporation, and raise salinity levels in soils 48. This can reduce forest productivity and biodiversity 49.
Stronger storms
Mangroves help reduce the impact of storms by slowing waves and storm surges 50. However, severe cyclones and hurricanes can also destroy mangrove forests 51. Extreme storms can uproot trees, break branches, strip leaves, and alter sediment patterns 52. Repeated disturbances may reduce biodiversity and slow forest recovery 53. Some mangrove species are more resilient than others and can regrow after storms 54.
Changes in rainfall and salinity
Climate change is altering rainfall patterns in many parts of the world 55.Reduced rainfall increases salinity in mangrove soils because less freshwater dilutes seawater 56. Extremely salty conditions can limit seedling survival, reduce tree growth, and transform mangrove areas into barren mudflats 57. On the other hand, increased rainfall may improve mangrove productivity in some regions by reducing soil salinity 58.
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