Agricultural chemicals are used to help grow crops and increase the growth of grass for grazing animals. These chemicals are fertilisers, herbicides to kill weeds and pesticide to kill or control animal pests. After rain, some of these chemicals will be washed into the local waterways and out to sea.
Heavy use of herbicide near waterways has been linked to some species of mangroves dying. It is not known how these chemicals affect the many kinds of animals that live in mangroves or if they impact on mangrove seedlings.