An emerging coastal wetland management dilemma between mangrove expansion and shorebird conservation

Coastal wetlands around the world have been degraded by human activities. Global declines in the extent of important coastal wetlands, including mangroves, salt marshes, and tidal flats, necessitate mitigation and restoration efforts. However, some well-meaning management actions, particularly mangrove afforestation, can inadvertently cause further loss and degradation of other habitats if these actions are not planned carefully. In particular, there is a potential conflict between mangrove and shorebird conservation because mangrove afforestation and restoration may occur at the expense of bare tidal flats, which form the main foraging habitats for threatened shorebirds and support other coastal organisms. We examined several case studies that illustrate the trade-off between mangrove restoration and bare tidal flat maintenance. To investigate whether these examples reflect an emerging broad-scale problem, we used satellite imagery to quantify the change in mangrove habitat extent in 22 important shorebird areas in mainland China from 2000 to 2015.The extent of tidal flat across all sites declined significantly (p < 0.01, n = 22) while among sites with mangroves present, the extent of mangroves expanded significantly (p < 0.01, n = 14). Our results suggest mangrove expansion and tidal flat loss have considerably reduced shorebird habitat in 8 of these sites. To improve the overall conservation outcome, we devised a decision tree for addressing the dilemma. Important factors to consider include whether the area of interest is of importance to shorebirds and what the potential impacts of mangrove expansion are; what the value of the proposed mangrove ecosystem is compared with the existing ecosystem; and that a conflict-resolution process will be needed if the choices are very similar With careful consideration of alternative management strategies, decision makers can ensure that the conservation of mangroves does not imperil migratory shorebirds.