by Charles Kennard
As artificial turf playing fields proliferate around Marin, the debate around artificial vs. natural grass largely revolves around installation and maintenance costs, the experience of human contact with materials, and year-round usage of the surface.
However, the environmental consequences of switching to artificial turf are considerable, and the long-term effects of emissions from the constituent materials have been little studied. The typical anatomy of artificial turf is this: at the bottom, a water-impermeable layer is created with clay and fabric; above it is a layer of rock, threaded by pipes that quickly drain the field; next is a fabric anchoring the synthetic blades of polyethylene or polyethylene blend; after all this has been assembled, the spaces between the blades are filled with recycled rubber crumbs, or with a cork and natural fiber mixture, to make the blades stand up and to provide cushioning.
Hydrology Natural turf fields in our area require approximately three-quarters of the wet season rainfall on them to sustain them through the summer, and this water must be captured in reservoirs elsewhere. However, water applied to natural turf fields can recharge local aquifers and provide some summer base flow to local creeks. Artificial fields require no water, but quickly shed rainfall into creeks and storm drains, contributing to flooding, and precluding groundwater recharge. This is important because less groundwater means lower summer flows in creeks.
Toxicity A study prepared for the Santa Clara Valley Water District in 2010 identified zinc released from recycled tires into drain water as a potential toxin to rainbow trout and to plant growth. On the other hand, pesticides and fertilizers applied to natural turf may well spread beyond the immediate area.
Disposal Artificial turf fields must be replaced about every 10 years (as was done at Drake High School in 2017), and the top layers of synthetic material added to a landfill. If the field is to revert to natural grass, then the potentially zinc-contaminated rock must also be dis-posed of safely. Even during the life-time of the artificial field, rubber particles spread to the surroundings.
Habitat Value Artificial turf fields have zero habitat value, and on hot days increase local air temperature. Natural mown grass provides at least a minimal opportunity for soil organisms, invertebrates, and some foraging or resting for birds.
Friends’ policy on playing fields in general can be found on our web-site under Reports and Policies