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 the carbon dioxide that is slowly warming the planet. Standing in the leafy reserve, shielded from the fierce sun, she says the Al-Qurm forest's 80 protected hectares (197 acres) of mangroves could lock away thousands of tons of CO2. IMAGES AND SOUNDBITES