In a muddy wetland in Oman's capital, environmental scientist Zakiya al-Afifi measures the bark of a mangrove tree and estimates its capacity to absorb carbon dioxide. Standing in the leafy reserve, she says the Al-Qurm forest's 80 protected hectares (197 acres) of mangroves could lock away thousands of tons of CO2. Oman, whose conservationist ruler Sultan Qaboos bin Said died in 2020, has become the Gulf's centre for mangrove restoration and conservation.