Some "green lawncare" practices can be harmful to aquatic life

Below, WRWEO Co-Chair David Patriquin comments on impacts of some "green lawncare" practices on aquatic life. The comments were published, with minor changes, as an op-ed in the Chronicle Herald on May 28th, 2011
under the heading "Lawn care restrictions still needed"

The widespread move to ban or limit the use of "cosmetic pesticides" in Canada has stimulated development of new products for "green lawncare", as well as new practices by lawncare franchises.

For the most part, these are positive and laudable responses to pesticide bans and consumer demand. However, there are some developing issues with the new materials and practices, especially in regard to their effects on aquatic life. Such effects deserve special attention in the Halifax Regional Municipality because of our many wetlands, lakes, streams and rivers, as well as coastal frontage.

The concerns:

1. Heavy use of organic fertilizers could stimulate algal blooms and excessive growth of aquatic plants though nutrient loading.

2. FeHEDTA (chelated iron), a synthetic chemical used to kill broadleaf plants, especially dandelion, is toxic to molluscs and crustaceans.

3. Pyrethrin, a natural pesticide used to kill pests, notably chinch bug in lawns, is toxic to crustaceans, tadpoles and some fish species.

4. Neem oil, a natural product applied to lawns to promote "plant health", is toxic to crustaceans, tadpoles and some fish species.

Whether such materials actually impact aquatic life depends on the quantities used and on the local environment. For example, impacts might be anticipated when a storm washes recent inputs to a lawn directly into a wetland or lake, or into a storm sewer that goes into a stream or lake.

We do have options for limiting such impacts, e.g., modest use of fertilizers, creating buffer zones, using nitrogen-fixing white clover to replace nitrogen inputs and compete with weeds. One lawn input could actually help freshwater life in areas where our lakes and streams have suffered from acid rain: lime. It's good for grass and clover and its good for early developmental stages of trout and salmon.

I think it's important that HRM retains its Pesticide By-law and its list of permitted materials (Administrative Order No. 23) so that we have maximum flexibility to address local issues within the overall framework of the provincial Non-essential Pesticides Control Act. An example: last week HRM Regional Council rejected a motion to include FeHEDTA in the list of permitted materials for HRM (Chronicle Herald May 25: Council bans new weed whacker). One argument for doing so: FeHEDTA is toxic to some aquatic life and the conditions that the Pesticide Management Regulatory Agency cites for low mobility and rapid breakdown of FeHEDTA may not apply very well in HRM. Council's rejection bucked a nationwide trend to approve use of FeHEDTA in jurisdictions with restrictions on cosmetic pesticides, the province of Nova Scotia amongst them.

HRM led the way in the development of pesticide restrictions and promotion of alternative materials and practices for lawn and garden care in large urban areas. With its rejection of FeHEDTA, HRM is leading the way towards refinements to protect the environment in jurisdictions that now restrict use of cosmetic pesticides and where new products and practices are being introduced.