Sea level rise caused by global climate change will leave coastal ecosystems more vulnerable to flooding. This will lead to increased soil salinity, a major abiotic stress that reduces plant growth. Seawater flooding alters the overall biogeochemistry of soils, limiting carbon sequestration and affecting greenhouse gas emissions and other ecosystem services. Restoration of saline soils can be achieved through phytoremediation, i.e. the use of salt-tolerant plant species that can sequester salt ions from saline soils. Yet limited information is available on tropical woody trees’ capacity to remove salt ions from the soil.
In a recent study published in AoBP, De Sedas et al. examined the salinity tolerance of 26 tropical tree species commonly found in coastal and inland wet forests of Panama. The authors found that whilst salinity tolerance varies greatly among tropical tree species, there was a close relationship between a species’ habitat and the ability to thrive under increasing salt concentration in the soil. As expected, coastal species were found to be better adapted to withstand increased soil salinity than non-coastal species. Coastal species such as Pithecellobium unguis-cati, Mora oleifera, Terminalia cattapa and Thespesia populnea maintained growth rates close to those of controls at 90 % seawater. In contrast, inland species such as Minquartia guainensis, Apeiba membranacea, Ormosia coccinea and Ochroma pyramidale showed strong reductions in growth rates and high mortality. The authors state that this study provides useful information about salinity tolerance among a significant group of tropical woody species and provides a first step towards formulating mitigation strategies for future sea-level rise. They suggest that further work should focus on salinity tolerance at a broader ecological scale to predict plant community shifts along exposed coastal areas.