Sustainable gardening

Sustainable gardens, landscapes and sites are a disparate group of horticultural interests that share, to a greater or lesser extent, the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature. Included within this compass are those home gardeners, and members of the landscape and nursery industries and municipal authorities, that integrate environmental, social and economic factors in an attempt to create a more sustainable future.

Historical development

Main articles: Sustainability and Sustainable development

After the establishment of sustainable agriculture in the early 1980s it was some time before the emergence of Sustainable Horticulture (as sustainable production horticulture) at the International Society of Horticultural Science's First International Symposium on Sustainability in Horticulture held at the International Horticultural Congress in Toronto in 2002. This symposium produced "conclusions ... on Sustainability in Horticulture and a Declaration for the 21st Century". The principles and objectives outlined at this conference were discussed in more practical terms at the following conference at Seoul in 2006

Many of the eco-friendly principles and ideas espoused by sustainable gardens, landscapes and sites perpetuate sustainable practices established as a reaction to resource-intensive industrial agriculture. These practices were established as movements for self-sufficiency and small-scale farming based on a holistic systems approach and ecological principles. Included here would be: biodynamic agriculture, no-till farming, agroecology, ecoagriculture, Fukuoka farming, forest gardening, organic gardening and others. On a larger scale there is the more recent "whole farm planning" which was established in 1995, ecoagriculture established in 2000, and other variants of sustainable agricultural systems. Retrieved on: 2009-03-16.

Integration of animals and gardens using permaculture

Perhaps the most influential of these approaches is permaculture, established by Australians Bill Mollison and David Holmgren as both a design system and a loosely defined philosophy or lifestyle ethic. Permaculture has, for David Holmgren become a whole-of-life pursuit integrating permaculture principles within a whole-of-life philosophy as indicated by the title of his 2002 publication Permaculture, principles and pathways beyond sustainability. Also in 2002 there was the initiation in Australia of the nursery industry based Sustainable Gardening Australia and the publication, in 2009, of the book “Sustainable Gardens” by staff at the Royal Botanic Gardens Melbourne.

Definition

The American Sustainable Sites Initiative is an interdisciplinary approach used by the American Society of Landscape Architects, the Lady Bird Johnson Wildflower Center and the United States Botanic Garden to create voluntary national guidelines and performance benchmarks for sustainable land design, construction and maintenance practices: it was founded in 2005. Using the United Nations Brundtland Report’s definition of sustainable development as a model, it defines sustainability within its own sphere of reference as:

… design, construction, operations and maintenance practices that meet the needs of the present without compromising the ability of future generations to meet their own needs

by attempting to:

...protect, restore and enhance the ability of landscapes to provide ecosystem services that benefit humans and other organisms.

A simpler definition applied to gardening is:

...gardening to maximize environmental benefit and human well-being.

The nursery-based Sustainable Gardening Australia has a more environmentally-based vision that:

... all Australians cultivate their gardens in sympathy with the environment by following the seasonal rhythms of the land, its ecology and its climate.

Principles & concepts

Managing global biophysical cycles and ecosystem services for the benefit of humans, other organisms and future generations has now become a global human responsibility. The method of applying sustainability to gardens, landscapes and sites is still under development and varies somewhat according to the context under consideration. However, there are a number of basic and common underlying biological and operational principles and practices in the sustainable sites literature.

Biological principles

Sustainable management of man-made landscapes emulates the natural processes that sustain the biosphere and its ecosystems. First and foremost is the harnessing the energy of the Sun and the cycling of materials thereby minimising waste and energy use.

Natural production and consumption

Planet Earth is essentially a closed biophysical system except for the input of energy from the Sun. The Sun's energy is stored by plants which, as primary producers, pass this energy (either directly or indirectly) through the food chain to all other organisms, the consumers. It is this energy that powers the biosphere as it is taken up by photosynthesis and released during respiration. This cycle of production and consumption is the basis of the fundamental biological cycle of birth, life, death, decay and renewal with the Sun providing the necessary energy to power the system. It follows that human influence on the simple components of this cycle of life, namely the carbon dioxide, water, nutrients and the plants that convert these substances to energy-rich food have the potential to have a major effect on sustainability and are therefore be monitored and managed with extreme care.

Biogeochemical cycles, ecosystem services and the natural economy

The physical processes of the biosphere and products of biological production and consumption that provide the goods and services on which all organisms depend can be referred to as the "natural economy". Humans especially depend on the ecological services of the natural economy for their health, prosperity and security.

Running within, and dependent on, the natural economy there is the production and consumption of goods and services in the “human economy” which has now significantly altered, in a detrimental way, natural biogeochemical cycles (notable here are the water cycle, carbon cycle and nitrogen cycle) so sustainable practices maximise support for ecosystem services.

Operational principles

Enhancement of ecosystem services is encouraged throughout the lifecycle of any site by providing clear design, construction, (operations), and management criteria. To be sustainable over the long term requires environmental, social and economic demands are integrated to provide intergenerational equity by providing regenerative sustainable systems. Operational guidelines will link to and supplement existing guidelines for the built environment (supplementing existing green building and landscape guidelines), the wider environment, and they will include metrics (benchmarks, audits, criteria, indexes etc.) that give some measure of sustainability (a rating system) by clarifying what is sustainable or not sustainable or, more likely, what is more or less sustainable.

Scale

Impacts of a site can be assessed and measured over any spatio-temporal scale or context.

Direct and indirect environmental impact

Impacts of a site may be direct by having direct measurable impacts on biodiversity and ecology at the site itself or indirect when impacts occur away from the site.

Site principles

• Do no harm
• Use the Precautionary principle
• Design with nature and culture
• Use a decision-making hierarchy of preservation, conservation, and regeneration
• Provide regenerative systems as intergenerational equity
• Support a living process
• Use a system thinking approach
• Use a collaborative and ethical approach
• Maintain integrity in leadership and research
• Foster environmental stewardship

Measuring site sustainability

One major feature distinguishing the approach of sustainable gardens, landscapes and sites from other similar enterprises is the quantification of site sustainability by establishing performance benchmarks. Because sustainability is such a broad and inclusive concept the environmental impacts of sites can be categorised in numerous ways depending on the purpose for which the figures are required. The process can include minimising negative environmental impacts and maximising positive impacts. As currently applied the environment is usually given priority over social and economic factors which may be added in or regarderd as an inevitable and integral part part of the management process. A home gardener is likely to use simpler metrics than a professional landscaper or ecologist. Factors that are considered include:

1. Sustainable Sites Initiative is producing recommendations for the American Landscape Industry . The standards and guidelines finally adopted will lead to a uniform national standard, which does not currently exist; Sustainable Sites will produce a rating system by 2011. The U.S. Green Building Council supports the project and plans to adopt the Sustainable Sites metrics into future versions of its Leadership in Energy and Environmental Design Green Building Rating System. Sites are rated according to their impact on ecosystem services: The following ecosystem services have been identified by the study group:

• Local climate regulation
• Air and water cleansing
• Water supply and regulation
• Erosion and sediment control
• Hazard mitigation
• Pollination
• Habitat functions
• Waste decomposition and treatment
• Global climate regulation
• Human health and well-being benefits
• Food and renewable non-food products
• Cultural benefits

2. Sustainable Gardening Australia and Sustainable Landscapes Australia. focus on key areas and categories of impact:

• Climate change
• Water conservation
• Invasive plants
• Biodiversity
• Chemicals
• Waste minimisation
• Organic waste
• Pollution prevention
• Renewable resources

3. Sustainable Gardens This applies systems thinking by viewing the site as an ecosystem unit of production and consumption. The site then becomes a system of processes and interactions with resource inputs and outputs. The sustainability ranking is then made by estimating resource inputs and outputs of the site, these then being scored according to their environmental influence both on and off site.

INPUTS

• Fossil fuels
• Embodied energy and water
• Compost
• Mulch
• Ecology & biodiversity
• Fertilizer
• Hard landscape materials
• Equipment
• Products

OUTPUTS

• Energy & water
• Food
• Green waste
• Ecology & biodiversity
• Chemicals
• Old hard landscape materials
• Old equipment
• Old products

PROCESSES

Constraints

Any kind of auditing or benchmarking will depend on the selection and weighting of the metrics chosen; the depth and detail of analysis required; the purpose for which the figures are required; and the environmental circumstances of the particular site.