This edition of The Overstory introduces some practical ways to use water from homes (from dishes, laundry, bathing, etc., NOT from toilets) as irrigation water for trees and landscapes. Rather than contaminate usable water by combining it with sewage, greywater systems keep dish and wash water separate from sewage and reuse it in the landscape. This is a classic means of "turning waste into a resource." This article is adapted from three publications by special guest author Art Ludwig, and introduces some of the practical concepts behind greywater reuse. For specific design and installation details for greywater systems, further study of the original publications is highly recommended.

What is greywater?

Any water that has been used in the home, except water from toilets, is called greywater. Dish, shower, sink and laundry water comprise approximately 80% of residential "wastewater." This may be reused for other purposes, especially landscape irrigation. Toilet-flush water is called blackwater. Contaminated greywater or wastewater that is difficult to handle, such as solids-laden kitchen sink water or water used to launder diapers, is sometimes called "dark grey" or blackwater. Reclaimed water (highly treated municipal greywater and blackwater, usually piped to large-volume users such as golf courses in a separate distribution system) is outside the scope of this article.

Farm forestry is the commitment of resources by farmers, alone or in partnerships, towards the establishment or management of forests on their land. To realise the full potential of farm forestry, avoid the temptation to promote or accept someone else's favourite or "pet" planting models. Farm forestry design should not be "top down" or "bottom up," but rather "inside out." Farmers and their communities need to be encouraged to look for opportunities whereby forestry can help solve their immediate needs while providing the prospect of generating the products and services that others are prepared to purchase.

Introduction

Designing farm forestry opportunities begins by asking the question: "Why would you want to grow or manage a forest?" The responses in any group of farmers will vary widely but can be loosely related to their financial, environmental, agricultural, non-agricultural or personal goals:

• Financial goals: investment, diversification, deferring income, utilising unproductive land, enhancing property values, providing on-farm employment, etc.
• Environmental goals: controlling land degradation, enhancing natural habitats, screening offensive industries, improving water quality, etc.
• Agricultural goals: shade and shelter, controlling vermin and noxious weeds, recycling or fixing soil nutrients, fodder for stock, etc.
• Non-agricultural goals: enhance tourism potential, develop new skills and job opportunities, establish a forestry related on-farm business, etc.
• Personal and lifestyle goals: wishing to leave a legacy, watch a forest grow, learn about the natural environment; improve the view, etc.

Genetic erosion is the loss of genetic diversity within a species caused by human activities and environmental changes. Unsustainable forestry practices and high rates of land clearance for agriculture are causing genetic erosion of valuable tree species in the tropics. This process endangers the economic sustainability of rural communities and limits opportunities for the development of new timber and non-timber forest products. With a focus on local community involvement, this article covers potential utility and limitations of six low-input interventions to help forestall further tree genetic erosion.

Introduction

"The first rule of intelligent tinkering is to keep all the pieces."--Aldo Leopold

The tropics have the highest tree species diversity in the world (Gentry and Ortiz 1993). For example, over 200 tree species (10 cm in diameter at breast height) per hectare have been recorded in parts of the upper Amazon (Gentry 1988). Tropical cultures are often heavily dependent on the many products and services these species provide: in a survey in the Peruvian Amazon, local farmers used more than 250 tree species and considered 155 of these as priorities for agroforestry (Sotelo-Montes and Weber 1997). In addition, numerous tropical tree species have promising national and international markets for fruit (Prance 1994; Villachica 1996), medicinal (Estrella 1995; Mejía and Rengifo 1995) and lumber products (Toledo and Rincon 1996). If appropriate cultivation techniques and markets were developed, these species could greatly assist in the economic development of some tropical regions (Anderson 1989; Castillo 1995; Leakey and Simons 1998).

Introduction

Mulch is a layer of decaying organic matter on the ground. Mulch occurs naturally in forests; it is a nutrient rich, moisture absorbent bed of decaying forest leaves, twigs and branches, teeming with fungal, microbial and insect life. Natural mulch stores the nutrients contained in organic matter and slowly makes these nutrients available to plants. Mulch also protects soil from desiccation by the sun and wind, as well as from the erosive effects of rain and run-off.

Mulch forms a necessary link in nutrient cycling vital for our soils. When mulch is absent for whatever reason, the living soil is robbed of its natural nutrient stores, becomes leached and often desiccates. Natural terrestrial environments without a litter layer are usually deserts. Non-desert plants grown in bare soil require constant fertilization, nutrient additions, and water, not to mention the work required to keep the soil bare.

"Sheet mulch" is a four-layered mulch system for use around crops. The four layers (or "sheets") mimic the litter layer of a forest floor, and optimize the weed control and fertility benefits of mulch. The sheet mulch technique described here is for use with trees or in gardens. The techniques can also be adapted for landscaping and other agricultural uses. Sheet mulch is a simple and underutilized technique protecting soil, reducing weed competition, and restoring fertility.

Introduction

Sustainable agriculture is a relatively recent response to the decline in the quality of the natural resource base associated with modern agriculture (McIsaac and Edwards 1994). Discussion of agricultural production has evolved from a purely technical one to a more complex one characterized by social, cultural, political and economic dimensions. The concept of sustainability is controversial and diffuse due to existing conflicting definitions and interpretations of its meaning. However, it is a useful concept as it addresses concerns about agriculture which are the result of the co-evolution of socioeconomic and natural systems (Reijntjes et al. 1992). A wider understanding of the agricultural context requires the study of agriculture, the global environment and social systems given that agricultural development results from the complex interaction of a multitude of factors. It is through this deeper understanding of the ecology of agricultural systems that doors will open to new management options more in tune with the objectives of a truly sustainable agriculture.

The sustainability concept has prompted much discussion and has promoted the need to propose major adjustments in conventional agriculture. Several possible solutions to the environmental problems created by capital and technology intensive farming systems have been proposed and research is currently in progress to evaluate alternative systems (Gliessman 1998). The main focus is the reduction or elimination of agrochemical inputs to assure adequate plant nutrition and plant protection through organic nutrient sources and integrated pest management.

A personal note from Bill Mollison

I have been vitally concerned about the environment for over thirty years, first as a scientist and naturalist, later as a vigorous campaigner against environmental exploitation.

As a child I lived in a sort of dream, and I didn't really awaken until I was about twenty-eight years old. I spent most of my early working life in the bush or on the sea. I fished and hunted for my livelihood. It wasn't until the 1950s that I noticed large parts of the system in which I lived were disappearing. First fish stocks became extinct. Then I noticed the seaweed around the shorelines had gone. Large patches of forest began to die. I hadn't realised until those things were gone that I'd become very fond of them; that I was in love with my country.

This discovery shifted the emphasis of my work in the late 1960s. This lead to the development of the "Permaculture Concept," a strategy which focuses on sustainable design for urban and rural properties. Permaculture, or PERMAnent CULTURE, is the conscious design of agriculturally-productive ecosystems and energy conserving settlements which have the resilience, dynamic stability and diversity of natural systems, like forests or grasslands. Such systems provide for their own needs, do not pollute or exploit, and are therefore sustainable in the long term.