Volumes have been written on the problem of invasive species. An invasive species is an animal or plant that has been introduced into an environment where it would not normally be. The transplanting can be either intentional or unintentional. An invasive species usually wreaks havoc with the local biome, since it has no natural predators in the new region. Much has been researched and written about invasive species, from rabbits introduced in Australia to Amazon Pacu fish introduced in Papua New Guinea.
The University of Minnesota recommends the topic of invasive species as worthy of investigation. One unbiased source of accurate information is the Environmental Protection Agency, which researches and presents information about the problem in the United States. One approach could be on efforts to eradicate invasive species.
Manmade "terraforming" is another idea worthy of writing about. In terraforming, whole areas of land and water are modified to suit a particular purpose. This has offshoot consequences for an area, and this subject can be explored and written about. For example, science editor Sharon Begley of "Newsweek magazine" stated that dams change the rainfall in the local environment. Because of the change, offshoot consequences are created. such as killing plants that do not tolerate excessive rain.
Pollution and its effects on the environment has been studied and written about extensively. Pollution is a very wide topic, but you can focus in on a particular segment, such as global warming caused by depletion of the ozone layer. Other topic areas could be how pollution affects ground water or toxic mercury levels in edible fish such as tuna. The EPA has researched mercury contamination extensively, and offers much information on mercury in fish.
You can write about a particular geographic biome, such as the Sahara desert or the Amazon rainforest. Other biomes include the Great Lakes, or the Great Plains states. You can write about the plants and animals found in a particular region, or the climate patterns of the area. Perhaps you could tie in other areas of investigation, such as how pollution affects the Great Lakes, or how "terraforming" changes the plant and animal life of a particular area.