Run-off from the watershed or drainage basin of a pond can carry with it materials detrimental to the longevity of a pond. Pollutants from a surrounding watershed advance aging of a lake or pond by creating excessive aquatic plant growth (a process known as advanced eutrophication). Advanced eutrophication is primarily caused by non-point source pollution, notably of nitrogen and phosphorus. This includes agricultural run-off from operating farms and excavated farm lands (new residential developments), run-off from lawn fertilizer use, livestock waste run-off, run-off from pet wastes, leaking septic systems, water fowl droppings, leaf litter, grass clippings, etc. Humans are the main cause of non-point source pollution. Rainfall can wash in large amounts of non-point source pollution into lakes and ponds.