Can Strict Protection Stop the Decline of Mangrove Ecosystems in China? From Rapid Destruction to Rampant Degradation

Abstract

China has lost about 50% of its mangrove forests from 1950 to 2001. Since 2001, mangrove forest area has increased by 1.8% per year due to strict protection of the remaining mangrove forests and large-scale restoration. By 2019, 67% of the mangrove forests in China had been enclosed within protected areas (PAs). In terms of the proportion of PAs of mangrove forests, China has achieved the conservation target of “Nature Needs Half”. The ongoing degradation of mangrove forests was assessed at the species, population, community and ecosystem levels. The results show that despite the strict protection, the remaining mangrove forests are suffering extensive degradation due to widespread anthropogenic disturbance. Of the 26 mangrove species, 50% are threatened with extinction, a proportion higher than the average for all higher plants in China (10.8%). Local extinction of some common species like Bruguiera gymnorhiza is widespread. About 53% of the existing mangrove areas were dominated by low-intertidal pioneer species. Consequently, the carbon stock in vegetation has decreased by 53.1%, from 21.8 Tg C in the 1950s to 10.2 Tg C in 2019. Meanwhile, there is an estimated 10.8% concomitant decrease in the carbon sequestration rate. The root cause for this degradation in China is seawall construction because most mangroves are outside seawalls in China. Without fundamental changes in protection and restoration strategies, mangrove forests in China will continue to degrade in spite of strict protection and large-scale restoration. Future mangrove conservation effort should aim to preserve the diversity of both the biota and the ecological processes sustaining the mangrove ecosystem. A few suggestions to raise the effectiveness of mangrove conservation actions were provided.

Mapping the Extent of Mangrove Ecosystem Degradation by Integrating an Ecological Conceptual Model with Satellite Data

“…Using information from published literature, we developed a conceptual model of mangrove ecosystems that assists in the identification of key pathways to mangrove degradation (Figure S1). In our analysis, we focused on degradation of mangrove vegetation due to its relative ease to be detected using satellites, though other aspects of the ecosystem may also represent mangrove degradation [36]. We used the conceptual model to identify satellite-derived variables and their ecological link to mangrove degradation (Table 1), helping us choose appropriate variables that are likely to change as a result of mangrove degradation.…”

“…Early studies estimated that 35% of the world's mangrove extent was lost between 1980 and 2000 [33], though the annual rate of mangrove forest loss slowed to an average of 0.26%-0.66% globally between 2000-2012 [34] and down to 0.13% between 2000-2016 [35]. However, remaining mangrove ecosystems are in various states of degradation as a result of a range of natural and anthropogenic disturbances, including seawall construction, clearing for agri-and aquaculture, overfishing, pollution, loss of tidal connectivity, and climate change related disturbances such as sea level rise and extreme climatic events [12,13,35,36]. Despite their importance and wide range of threats they face, many remote sensing studies focus primarily on mapping mangrove ecosystem distribution and extent.…”

Mangrove Restoration under Different Disturbances Regime in the Niger Delta, Nigeria

“…1. Disturbance: is a change in environmental conditions that disrupts the functioning of an ecosystem [26]. Disturbance can occur at a variety of spatial and temporal scales, and is a natural component of many communities.…”

Spatially non-continuous relationships between biological invasion and fragmentation of mangrove forests

“…Regional governments have also taken actions into mangrove conservation. For example, Chinese government has established twenty-eight Protection Areas, which has protected 67% of the mangrove forests in China (Wang et al, 2020). The key way to achieve these goals is mangroves planting.…”