Constant monitoring allows biologists to recognize problems and trends. Frequently, clean-up procedures are initiated to improve harmful situations. Sometimes consumption advisories are issued to protect people from eating too much of a resource that may have high levels of substances dangerous to human health. For example, high mercury levels, and many other contaminants, have been documented in fish and ducks collected from San Francisco Bay National Wildlife Refuge in California. People have been advised not to eat sport fish and waterfowl of certain species near this area.
Most monitoring takes place in cooperation with other federal agencies.