.png)
MANGROVE DEFORESTATION
Mangrove forests in the Mekong Delta are distributed along nearly the entire coastline, extending approximately 720 km, with major concentrations in the provinces of Ca Mau, Bac Lieu, Soc Trang, Tra Vinh, Tien Giang. Prior to 1975, the total mangrove area was estimated at around 250,000 hectares; however, it has since declined to approximately 150,000–180,000 hectares, representing a loss of nearly one-third to one-half. In addition to the reduction in extent, forest quality has also significantly degraded. Many existing areas now consist primarily of planted mangroves, characterized by lower tree density, reduced height, and smaller biomass compared to natural forests, resulting in diminished ecological functions, particularly in terms of coastal protection.
The drivers of mangrove degradation are not limited to anthropogenic activities (such as land conversion, infrastructure development, and logging), but are also strongly influenced by basin-scale changes. Most notably, there has been a substantial decline in sediment supply from the upstream Mekong River, estimated at approximately 70–80%, primarily due to the combined effects of hydropower dam construction and sand mining. Sediment deficiency prevents the replenishment of coastal and sub-canopy soils, limiting natural forest regeneration. At the same time, the substrate becomes increasingly unstable, making mature trees more susceptible to uprooting under wave and current forces.
In addition, the combined effects of sea-level rise and land subsidence have led to an increase in relative sea level along the coast. As water depth increases, wave energy can propagate further inland into the forest rather than being dissipated at the seaward edge. This process often results in severe erosion at the seaward margin (toe erosion), leading to shoreline retreat, whereby the entire mangrove belt gradually shifts landward. This has become one of the most prevalent mechanisms of mangrove degradation in the Mekong Delta.
Functionally, mangrove forests act as highly effective “biological barriers” for wave energy reduction. Studies indicate that mangroves can attenuate between 50% and 90% of incoming wave energy before it reaches the shore. When mangroves are degraded or lost, wave energy directly impacts the coastline, significantly increasing erosion rates. In fact, many coastal areas in the Mekong Delta have transitioned from accretionary to erosional states, with typical erosion rates ranging from 10 to 30 meters per year, and even higher in certain hotspots.
Beyond wave attenuation, the dense root systems of mangroves play a critical role in trapping and accumulating sediments. By reducing flow velocity, mangroves facilitate the deposition and gradual buildup of suspended sediments, contributing to land elevation gain and enhancing resilience to sea-level rise. When mangroves degrade, this mechanism is disrupted, reducing the delta’s capacity for natural vertical accretion and thereby increasing long-term flood risk.
Beyond wave attenuation, the dense root systems of mangroves play a critical role in trapping and accumulating sediments. By reducing flow velocity, mangroves facilitate the deposition and gradual buildup of suspended sediments, contributing to land elevation gain and enhancing resilience to sea-level rise. When mangroves degrade, this mechanism is disrupted, reducing the delta’s capacity for natural vertical accretion and thereby increasing long-term flood risk.