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USGS2024

Coastal wetlands in the Anthropocene

We review the functioning and sustainability of coastal marshes and mangroves. Urbanized humans have a 7,000-year-old enduring relationship to coastal wetlands. Wetlands include marshes, salt flats, and saline and freshwater forests. Coastal wetlands occur in all climate zones but are most abundant in deltas. Mangroves are tropical, whereas marshes occur from tropical to boreal areas. Quantification of coastal wetland areas has advanced in recent years but is still insufficiently accurate. Climate change and sea-level rise are predicted to lead to significant wetland losses and other impacts on coastal wetlands and the humans associated with them. Landward migration and coastal retreat are not expected to significantly reduce coastal wetland losses. Nitrogen watershed inputs are unlikely to alter coastal marsh stability because watershed loadings are mostly significantly lower than those in fertilization studies that show decreased belowground biomass and increased decomposition of soil organic matter. Blue carbon is not expected to significantly reduce climate impacts. The high values of ecosystem goods and services of wetlands are expected to be reduced by area losses. Humans have had strong impacts on coastal wetlands in the Holocene, and these impacts are expected to increase in the Anthropocene.

Annual Review of Environment and Resources↗

USGS2017

New interventions are needed to save coral reefs

Since 2014, coral reefs worldwide have been subjected to the most extensive, prolonged and damaging heat wave in recorded history1. Large sections of Australia’s Great Barrier Reef (GBR) bleached in response to heat stress in 2016 and 2017 — the first back-to-back event on record. Such severe coral bleaching results in widespread loss of reef habitat and biodiversity. Globally, we are facing catastrophic decline of these ecosystems, which sustain services valued at around $US 10 trillion per year2, are home to over a million species3, and feed and support the livelihoods of hundreds of millions of people4. Model predictions indicate that mass coral bleaching could become the new norm by 2050 (ref. 5). Critically, even if global warming can be kept within 1.5⁰C above preindustrial levels, shallow tropical seas would warm at least 0.4°C in coming decades, triggering frequent bleaching of the most sensitive habitat-forming coral species6. This outlook poses a time-critical decision challenge for management and conservation. Existing conservation approaches, despite innovative governance arrangements7, could simply become insufficient to protect coral reefs under any expected climate future. Thus, for coral reefs to remain resilient and their services sustained, we argue that new and potentially riskier interventions must be implemented alongside conventional management efforts and strong action to curb global warming. We build the case for this strategy below.

Nature Ecology & Evolution↗