Ecosystems Ecology 12 Pollution 6 Aquatic Biology and Ecology 5 Biodiversity 4 Biology 4 Environmental studies 4 Land resources 4 Mineral resources 4 Plants 4 Water resources 4 Disaster management 3 Energy resources 3 Eutrophication 3 Fishery management 3 Food resources 3 Forest resources 3 Lakes 3 Marine ecology 3 Natural resources 3 Pollution and Degradation 3 Renewable resources 3 Sustainability 3 Trees 3 Water Resources 3 Woody plants 3 Agriculture 2 Aquacultural and Fisheries Economics, (New March 2000) 2 Climate 2 Climatic change 2