Ecology isn't an esoteric academic field. Topics such as global warming, pollution, acid rain and oil spills can affect the present as well as the future. Select a debate within the field of ecology, and offer research to support your opinion. For example, you might argue that coal mining is not a good substitute for oil because of the ecological havoc mines can wreak.
The Earth is filled with diverse and highly complex ecosystems. Even a spoonful of soil contains lots of interactions between various organisms. Pick an ecosystem -- the size of which should be determined by the length and depth of your paper -- and elaborate on the roles that various organisms play in that ecosystem. You might also address the way human interventions have affected the ecosystem. For example, the Great Barrier Reef has suffered as a result of pollution.
Ecologists frequently attempt to devise novel solutions to ecological challenges. Try writing about how to address one such challenge. For example, you might analyze data to determine the ecological impact of mass transit and, if the numbers are favorable, show how high-speed rails could positively impact local ecosystems. Alternatively, you could address the way individual choices either benefit or harm ecosystems.
Ecological systems are heavily affected by new technologies. Try addressing how one such technology could affect the environment. For example, fossil fuels have overwhelmingly negative effects, but algae could be a cheaper, safer and renewable fuel option. Try interviewing an expert or examining the ways such technologies have affected one specific ecosystem.