Conservation conundrum – Red listing of subtropical-temperate coastal forested wetlands of South Africa

Abstract

Africa’s range-restricted and transitional subtropical-temperate coastal forested wetlands are facing interlinking threats of climate and anthropogenic pressures. We assessed their conservation status using the criteria of the International Union for Conservation of Nature (IUCN). Their total areal extent was hind-casted to the reference epoch 2000, followed by the quantification of subsequent total losses in areal extents for the epochs 2005, 2008, 2011 and 2017. South Africa had 120 km2 of coastal swamp and floodplain forests in 2000 of which the majority (116.5 km2) occurred on the Maputaland Coastal Plain (MCP). By 2011, 20% of the areal extent was lost, and at the lowest rate of decline we estimate that ≥ 80% of the rest will be lost in the next 50 years. An ecosystem collapse assessment therefore indicated that the habitat is very likely Critically Endangered. Fragmentation and types of transformations were used as degradation indices to show functional collapse. These results showed that forest patches became increasingly fragmented, from 511 to 1 145 patches between 2000 and 2017 and that > 23% of the areal extent showed severe transformation. Several faunal species, with a close association to the forested wetlands of the MCP, are considered threatened with numbers declining because of transformation to timber plantations or agriculture and coupled with a prolonged drought. Of these, a sub-species of the Samango monkey, Cercopithecus mitis erythrarchus, considered to be a primary ecosystem engineer of the habitat, was red listed with a restricted distribution, being endemic, Near Threatened and declining. Also under pressure, because of habitat fragmentation and degradation is the Peregrine crab (Varuna litterata), a euryhaline species requiring connectivity across the land-seascape, ranging from freshwater forested wetlands to estuarine and off-shore environments. Functionally, these coastal forested wetlands are therefore also considered Critically Endangered. The final IUCN conservation status of South Africa’s subtropical-temperate coastal forested wetlands are recommended to be very likely Critically Endangered. Irrespective of 62% of the areal extent of these forested wetlands being within protected areas, severe degradation (metrics of fragmentation and transformation) were observed even inside these areas for the past two decades. The conservation conundrum is that despite existing legislation and management measures, there has been no stop or reversal of the negative trends to date. As a supplementary method, we therefore recommend a transdisciplinary community-based approach to conservation practice, continued and improved monitoring of the habitat losses, the identifying priority areas for rehabilitation and addressing data deficiencies in important species associations.

Keywords

• Ecosystem risk assessment
• Fragmentation
• Habitat collapse
• IUCN transitional forested wetlands
• Red listing of ecosystems
• Swamp and floodplain forests