The Impact of Lawns on Lakes

The late Stan Dobson, a famous limnologist with a practical interests, gave a talk in 2007 about the measured impact of lawns on water quality in the Madison, WI area. He found that of all the watershed factors one could correlate with measures of water quality, the one that explained the greatest portion of variation in nutrient levels, algae blooms, and loss of species diversity was the percent of the watershed in lawn. Now not all lawns are created equal, and having a grassy area associated with a home or business is not always the worst thing the owner can do, but the tendency to fertilize lawns and the substantial probability that the associated nutrients will reach a downstream waterbody are what make this correlation so strong. Lawns are a very real problem for lakes. They don’t have to be, but they are because of societal “pressure” to manage them in ways that are not good for lakes.

The nutrient issue is exacerbated by lawn care companies that over-fertilize (the chemicals cost less than the labor to retreat if results are unacceptable) and do not scientifically adjust the ratio of nutrients to fit each treated area (can you imagine a lawn care professional in a white lab coat testing soil content before deciding what mix of fertilizer to apply?). People doing lawn care on their own may not be any more responsible. This has resulted in a big push to get phosphorus out of lawn fertilizers, as most established lawns do not need more, and enough towns and even states have banned the use of high P fertilizer on lawns to get the fertilizer manufacturers to voluntarily reduce P content. Measured changes in downstream waters, including some peer reviewed literature (including 2 papers in Lake and Reservoir Management that are freely available), show a significant decrease in P concentration as a result. We still have issues with applied pesticides and nitrogen, but at least the over-application of P is on the wane.

But there is more to lawns than just chemical additives. Creation of lawn to the water’s edge, either at the lake or on any of its tributaries, eliminates buffers for nutrients, sediment, and anything else on the lawn (naturally, not just from additions) and increases loading to lakes. Loss of shoreline structure has been demonstrated (again, check out papers in Lake and Reservoir Management) to reduce species diversity and hurt fish communities and fishing. Loss of vegetative structure away from the water has known negative impacts on terrestrial ecology as well (hey, we can’t be totally lake-centric!). In short, lawns are not good for the environment. They don’t have to be measurably bad, but there is very little to be said in their favor from an ecological or water management viewpoint.

This does not mean that all responsible owners should do away with all lawn area, but it does mean that we should think twice about how much lawn we create and how we manage it. Bob Kirschner of the Chicago Botanical Garden and some other folks associated with NALMS have given some great presentations on how far you can take ecological landscaping before you are perceived as an “irresponsible” citizen of the community by those who look at lawns and landscaping as the taming of nature and a sign of culture. And it is a lot further than many lakefront property owners have gone. Yet there are some great examples out there of ecologically sensitive landscaping and more seem to be popping up all the time. The Maine program called Lake Smart espouses this approach and is achieving some success. New Hampshire and more recently Vermont have shoreland protection legislation that helps, but there is a major need for an education component to attain success, rather than just enforcement. We need to change the way that society perceives developed landscapes, with a focus on lessening impacts on our water resources.