A free email agroforestry journal for practitioners, extension agents, researchers, professionals, students, and enthusiasts. One edition is sent each month focusing on a concept related to designing, developing, and learning more about trees and agroforestry systems. Focuses on trees and their roles in agriculture, natural ecosystems, human culture and economy.

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Overstory #244 - Self-renewing fertility in edible forest gardens

Forested landscape at Chrystal Waters, Queensland, Australia.Many characteristics of forest gardens support self-renewing fertility.


The forest-gardening approach to fertility emphasizes strategies employed in the design phase that should reduce the need for work and expensive inputs later on down the line. Many basic characteristics of forest gardens support self-renewing fertility by their very nature: perennial plant roots provide consistent root-zone resources to the soil food web; lack of tilling allows undisturbed development of the soil organism community; consistent mulch provides stable food resources for the decomposers and a stable soil environment for everyone who lives down there; and so on.

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Overstory #243 - Introduction to Globally Important Agricultural Heritage Systems-

Ifugao Rice Terraces (photo: FAO)The ancient Ifugao rice terraces of the Philippines are supported by indigenous knowledge management of muyong, a private forest that caps each terrace cluster and provides a biodiversity reserve and watershed functions. (Photo © FAO)


For millennia, communities of farmers, herders, fishers and forest people have developed complex, diverse, and locally adapted agricultural systems. These systems have been managed with time-tested, ingenious combinations of techniques and practices that have usually led to community food security, and the conservation of natural resources and biodiversity. Agricultural heritage systems can still be found throughout the world covering about 5 million hectares, which provide a vital combination of social, cultural, ecological and economical services to humankind. These “Globally Important Agricultural Heritage Systems-GIAHS” have resulted not only in outstanding landscapes of aesthetic beauty, maintenance of globally significant agricultural biodiversity, resilient ecosystems and a valuable cultural heritage. Above all, these systems sustainably provide multiple goods and services, food and livelihood security for millions of poor and small farmers. The existence of numerous GIAHS around the world testifies to the inventiveness and ingenuity of people in their use and management of finite resources, biodiversity, ecosystem dynamics, and ingenious use of physical attributes of the landscape, codified in traditional but evolving knowledge, practices and technologies. Whether recognized or not by the scientific community, these ancestral agricultural systems constitute the foundation for contemporary and future agricultural innovations and technologies. Their cultural, ecological and agricultural diversity is still evident in many parts of the world, maintained as unique systems of agriculture. Through a remarkable process of co-evolution of Humankind and Nature, GIAHS have emerged over centuries of cultural and biological interactions and synergies, representing the accumulated experiences of rural peoples.

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Overstory #242 - What is a forest garden?

Schematic drawing of forest gardenEvery forest garden is different because they are designed around the needs and requirements of their users. (Illustration: C. Sobel)


A forest garden is a garden modelled on the structure of young natural woodland, utilising plants of direct and indirect benefit to people - often edible plants. It may contain large trees, small trees, shrubs, herbaceous perennials, herbs, annuals, root crops and climbers, all planted in such a way as to maximise positive interactions and minimise negative interactions, with fertility maintained largely or wholly by the plants themselves.

The plants in a forest garden are mainly perennial, which gives the system its long-term nature. Many of the plants used are multipurpose; they may have a main function or crop but will very often also have a number of other uses. Plants are also mixed to a large degree, so there are few large blocks or areas of a single species, and each species is grown close to many others in ways that are mutually beneficial.

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Overstory #241 - Forests for improved food and nutritional security

Tropical homegarden in 'Upolu, Samoa.Forests as well as trees on farms are a direct source of food and cash income for more than a billion people.

Food and nutritional security – a growing global challenge

Feeding the world’s population is one of the most pressing challenges facing humanity in the twenty-first century. FAO estimates that 925 million people in the world are food insecure, representing around one in six of the world’s population. Spiralling food prices in 2006 and 2007 resulted in food riots in 22 countries as poor households found it increasingly difficult to cover basic food needs. At the Millennium Development Goal (MDG) Summit held in New York in September 2010, countries reaffirmed their commitment to reaching the MDGs, including the eradication of extreme poverty and hunger. Under this goal, there is a commitment to halve the proportion of people who suffer from hunger by 2015.

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Overstory #240 - Microclimate management and manipulation aspects of applied agroforestry

Tropical homegarden in 'Upolu, Samoa.Alley cropping with nitrogen fixing trees (Calliandra calothyrsus) growing on the contour, with jackfruit (Artocarpus heterophyllus) trees in between.

Farming systems we need

For quite some time we have been aware that the solution to improved crop productivity does not only rely on mechanized rotational monocropping systems used in developed countries such as North America and Western Europe, but also on the polyculture cropping systems traditionally used in developing countries such as in Africa and Latin America (e.g. Francis and Adipala 1994). A new debate is emerging across the world about the future agriculture at a time of food, fuel and financial crises. We need to foster an agriculture that is inclusive, multifunctional, and built on principles of resilience that are crucial in the process of adapting to climate change (LEISA 2008). We need farming systems that will increase food security, decrease environmental impact, respond to climate change and provide management alternatives that will enhance natural resource use, provide stable and high returns to the farmer. There is trade-off between agricultural benefits and environmental costs (see also Palmer 2008 and Box I).

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Overstory #239 - The Benefits of Tropical Homegardens

Tropical homegarden in 'Upolu, Samoa.Tropical homegardens can benefit community, economic, and ecological systems.

What is a Tropical Homegarden?

A traditional tropical homegarden (THG) of the Pacific Islands differs greatly from the raised bed or vegetable patch image commonly associated with temperate home edible gardens. A THG is a small-scale agroforestry land use system based on cultural traditions of subsistence living. A THG is in close proximity to a place of residence and tended to by the household members. Plants are grown for personal consumption as food, as well as for medicinal, ceremonial and construction purposes.

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