Climate-friendly gardening

[6] The three main greenhouse gases produced by unsustainable land use are carbon dioxide, methane, and nitrous oxide.

[4][7] Black carbon, or soot, can also be a product of unsustainable land use, and, despite not being a gas, it can behave like greenhouse gases and contribute to climate change.

[6] Gardeners may cause extra carbon dioxide to be added to the atmosphere in several ways: Methane, CH4, is a natural part of the carbon cycle, but human land uses often add more, especially from anaerobic soil, artificial wetlands such as rice fields, and from the guts of farm animals, especially ruminants such as cattle and sheep.

[22] Gardeners may cause extra methane to be added to the atmosphere in several ways: Nitrous oxide, N2O, is a natural part of the nitrogen cycle, but human land uses often add more.

[6] A climate-friendly garden therefore does not contain large irrigated lawns, but instead includes water-butts to collect rainwater, water-thrifty plants which survive on rainwater and do not need watering after they are established, trees, shrubs and hedges to shelter gardens from the drying effects of sun and wind, and groundcover plants and organic mulch to protect the soil and keep it moist.[2][4][5]p. 242[12]p.

[41] Climate-friendly gardens therefore include: Lawns, like other grasslands, can build up good levels of soil carbon,[41] but they will grow much more vigorously and store more carbon if besides grasses, they also contain nitrogen-fixing plants such as clover,[4] and if they are cut down using a mulching mower which returns finely-chopped mowings to the lawn.

More carbon, however, may be stored by other perennial plants such as trees[12] and shrubs and they also do not need to be maintained using power tools.

[40] Other sources of greenhouse gases from farmland include: compaction caused by farm machinery or overgrazing by farm animals can make soil anaerobic and produce methane, which is emitted during the production and transport of coal, natural gas, and oil.

Methane emissions also result from livestock and other agricultural practices, land use and by the decay of organic wastes in municipal solid waste landfills; farm animals produce methane; and nitrogen fertilizers can be converted to nitrous oxide which is also emitted during agricultural, land use, and industrial activities; combustion of fossil fuels and solid wastes; as well as during treatment of wastewater.

[48][49] Climate-friendly gardeners therefore grow at least some of their food,[12] and may choose food crops which therefore help to keep carbon in farmland soils if they grow such high-risk crops in small vegetable plots in their gardens, where it is easier to protect the soil than in large fields under commercial pressures.

Climate-friendly gardeners may grow and eat plants such as sweet cicely which sweeten food, and so reduce the land area needed for sugar-beet.

[50] They may also choose to grow perennial food plants to not only reduce their indirect greenhouse gas emissions from farmland, but also to increase carbon stores in their own gardens.

[39][50][51][52] Grassland contains more carbon per hectare than arable fields, but farm animals, especially ruminants such as cattle or sheep, produce large amounts of methane, directly and from manure heaps and slurry.

[28][53] Gardeners who want to reduce their greenhouse gas emissions can help themselves to eat less meat and dairy produce by growing nut trees which are a good source of tasty, protein-rich food, including walnuts which are an excellent source of the omega-3 fatty acid alpha-linolenic acid.

[12] In particular, they try to avoid or reduce their consumption of tapwater because of the greenhouse gases emitted when fossil fuels are burnt to supply the energy needed to treat and pump it to them.

Climate-friendly gardeners will also aim to follow "cradle-to-cradle design" and "circular economy" principles: when they choose to buy or make something, it should be possible to take it apart again and recycle or compost every part, so that there is no waste, only raw materials to be made into something else.

In place of a water-thirsty lawn that requires a lot of fertilizers and herbicides to be kept green and weed-free, native vegetation may be planted.

Climate-friendly gardeners will therefore use their greenhouses carefully by: Climate-friendly gardeners will not put woody prunings on bonfires, which will emit carbon dioxide and black carbon due to the high oxygen content of such fires,[5] but instead burn them indoors in a wood-burning stove and therefore cut emissions from fossil fuel, or cut them up to use as mulch and increase soil carbon stores,[12] make biochar by pyrolysis,[15] or add the smaller prunings to compost heaps to keep them aerated, reducing methane emissions.

Climate-friendly gardeners may choose instead to use nitrogen-fixing plants which will add nitrogen to the soil without increasing nitrous oxide emissions.