Several of the causes and manifestations of Climate Change could have serious consequences for community gardens including higher CO2 levels, warmer temperatures, higher or lower than normal precipitation and severe or unusual weather events.
Higher levels of carbon dioxide (CO2) in the atmosphere is one of the major causes of the greenhouse effect which generally raises average yearly temperatures. Another effect of higher CO2 levels, faster plant growth, has both a positive and negative effect on plants. A study published in 2012 showed that trees in New York City grew significantly faster in the urban environment than in rural areas. Now this is true for above ground biomass but at the same time the roots grow more slowly and the wood produced by the faster growing trees is a weaker wood. Warmer temperatures particularly at night accounted for some part of the faster growth. Both higher CO2 levels and higher temperatures are factors in the Heat Island Effect experienced in urban areas and could be looked at as both cause and effect of climate change.
Community gardens can help reduce the Heat Island effect as the temperature can be several degrees cooler in a community garden than on the asphalt covered streets and concrete sidewalks just outside of the garden. This phenomena of faster plant growth can in the case of vegetables grown in community gardens (or even on farms) results in increased yields but at the expense of lower nutrient content.
Higher temperatures can mean a greater need for irrigation as plants will dry out more quickly. Weeds can also grow faster which can create additional weeding work and can stunt the growth of the plants we want to grow. Some pests can also thrive in the higher temperatures or have an additional generation during the growing season. Community Gardeners can also be impacted by higher temperatures as the elderly, those with compromised immune systems or with chronic diseases are compromised during heat waves or just can't be out in the heat.
Most of the United States has experienced drought in the last decade, in some cases longer. Scientists are making the connection between drought and climate change particularly instances of severe drought. Drought conditions can put stresses on plants causing decreased yields or pest problems. In drought situations, increased watering or irrigation can put extra pressure on the local water supply. In community gardens, the use of water conservation techniques helps alleviate drought stresses. So most community gardens have adapted to drought conditions by using drought tolerant plants, mulch, compost, drip irrigation and rainwater harvesting . Unfortunately rainwater harvesting can't help very much if it doesn't rain at all.
A number of gardens in NYC know first hand the effects of severe and unusual weather events. The community gardens that were damaged by Superstorm Sandy needed time, labor, materials and money to rebuild after being flooded by contaminated water or destroyed by falling tree limbs or complete trees. Sandy happened in 2012 and the community gardeners are still working toward making their gardens resilient. A good source of techniques to help make a community garden is this resilient community garden manual .
Community Gardening and community gardeners have a very real symbiotic relationship with climate change. The manifestations of climate change can have serious impacts on the ability of community gardens to survive. Community gardeners, just by being stewards of green spaces that help to mitigate climate change, find ourselves on the front lines as part of the solution that might just put the brakes on climate change.
