Overstory #72 - Microenvironments (Part 1)
Agroforestry systems are often characterized by diversity and complexity. This includes a diversity of microenvironments (small-scale environments different from their surroundings, such as deep shade under a tree canopy). In this edition of The Overstory, guest author Robert Chambers discusses the importance of microenvironments to sustainable livelihoods.
Most agriculture creates or alters environments, through ploughing, irrigation, the effects of crop canopies, effects of grazing and browsing, and so on. A microenvironment (ME) is a distinct small-scale environment which differs from its surroundings, presenting sharp gradients or contrasts in physical conditions internally and/or externally. Microenvironments can be isolated, or contiguous and repetitive. They can be natural, or made by people or domestic animals.
Examples of Microenvironments (MEs)
- clumps, groves or lines of trees or bushes
- sheltered corners or strips, protected by aspect of slope, configuration, etc.
- springs and patches of high groundwater and seepage strips, and pockets of impeded drainage
- home gardens (also known as household, kitchen, backyard or dooryard gardens)
- vegetable and horticultural patches (protected, with wells, etc.)
- river banks and riverine strips
- levees and natural terraces
- valley bottoms
- wet and dry watercourses: streams, dry river beds, drainage lines
- alluvial pans
- artificial terraces
- silt trap fields (depositional fields, gully fields, etc.)
- raised fields
- ditches or ponds (especially in wetlands)
- water harvesting in its many forms
- hedges and windbreaks
- pockets of fertile soil (old termite mounds, former livestock pens, etc.)
- plots protected from livestock
- flood recession zones
- small flood plains
- lake basins
- ponds, including fishponds
- animal wallows (e.g. for buffalos or pigs)
Apart from personal observation, the main sources for this listing are Richards, 1985; Pacey with Cullis, 1986; Altieri, 1987; Harrison, 1987; Wilken, 1987; and IIED, 1989.
Properties of Microenvironments
There are a number of important properties and functions of MEs.
Because MEs differ from their more uniform surroundings, their use also usually differs. An example is paddy grown in silt deposition fields in nallahs in semi-arid India. But specialisation, though general, is not universal. Some gully fields in Ethiopia are used to crow the same crop - sorghum - as in neighbouring more extensive fields though, it can be expected, with higher yields and lower risk.
Farmers' own soil and water 'conservation' is often soil, water, and nutrient 'concentration'. Soil concentration occurs when soil or silt is dug from common land and carted to build up fields and fertility. Erosion is exploited for the low cost transport it provides for silt which is then trapped by rocks, brushwood, trash lines, vegetative barriers or earth bunds. Water concentration occurs when it is channelled, captured and retained in water harvesting. Nutrient concentration occurs through silt deposition, farm yard manure in and near homesteads and in livestock pens, leaf litter under bushes and trees, and organic manures carted to the ME site. These forms of soil, water and nutrient concentration interact synergistically (see e.g. Kolarkar et al., 1983).
For domestic and wild animals, many MEs present attractive islands of green in dry expanses and they are therefore vulnerable to grazing and browsing. Protection is essential except where, as with some eucalypts, plants are unpalatable. Fences, hedges, and barriers are necessary and common. Difficulties in protection against animals can deter the creation or exploitation of MEs or determine what is grown in them. As for climate, many MEs are protected to create their own microclimates, often sheltered from excessive sun, wind and/or water.
Diversity and Complexity
Diversity in species of plant and animal, and complexity in biological relationships between them, are common in MEs. Multiple canopies, agroforestry combinations, vining plants, variety of species, and plants at various stages of growth are common characteristics. The movement and arrangement of soil and stones often make the land surface less even and more varied. The untidiness of some MEs incorporates a large number of interactions.
Nutrition and Health
Apart from the quantity and relative stability of the flows of food and income to households, MEs (especially home gardens) provide two other benefits: medicinal plants, and vegetables, fruits, and other foods for diversified diets which also include more vitamins. Findings of dramatic drops in child mortality with vitamin A supplementation (a 60% reduction in a study near Madurai in South India, and a 45% reduction in a study in Indonesia (pers. comm. Saroj Pachauri)) point to the key potential of home gardens as a source of life-saving vitamins.
Reserves and Fallbacks
MEs frequently provide reserves to meet contingencies, and for lean seasons and bad years. Trees to which people have clear rights increasingly serve as savings banks which can be cashed to meet seasonal or sudden needs (Chambers and Leach, l989). A very poor family in Kakamega District in Kenya had in 1988 a line of Eucalyptus at the bottom of their half acre plot which they cut and sold in the lean times of February and March to buy food and soap. In Sudan, wadi cultivation is especially significant in bad years (pers. comm. Ian Scoones). In Zimbabwe, key resource habitat patches are important for cattle in bad years (Scoones, 1988). Leaf fodder from trees on private land was used by some farmers in Gujarat as their last fallback for feeding their livestock during the great drought of 1987-8. By accumulating reserves of value, and by providing output which lasts longer, MEs thus contribute to the sustainablity of livelihoods.
Following the analysis of Ester Boserup (1965), the technology used in agriculture (in this case for MEs) is related to population pressure and labour availability. MEs will then be increasingly developed and exploited as population pressure increases. In some environments there may be a critical phase when more labour is needed to develop, protect, maintain, and exploit them. When paths diverge, either people migrate (seasonally or permanently) and leave an unsustainable and risky farming system; or, they stay and invest in mote sustainable intensification. One illustration is water harvesting near Yatenga on the Mossi Plateau in Burkina Faso where investment of labour in laying out rock bunds and digging pockets for crops has led to higher and more stable production and reportedly less outmigration. MEs greater productivity, stability, and spread of production period can thus locally support more livelihoods.
Innovation, Experiment and Adaptability
MEs play a vital part in innovations, experimentation and adaptation. Some wild plants which are candidates for domestication are tried first in home gardens. Anil Gupta reports that a survey by women scientists in Bangladesh identified a large number of innovations in homegardens (Gupta, 1989). Calestous Juma notes that farmers place such plants first in environments similar to those where they were found, for example in moist ground near a stream (Juma, 1989) and gradually move them out into harsher environments. Paul Richards observes for West Africa that when farmers carry out experiments, they typically begin in the neglected run-off zone (Richards, 1985). Indeed, the past failure to observe farmers' experiments may partly stem from the failure to notice the MEs in which they are to be found. MEs thus contribute to the sustainability of livelihoods by providing locations for experiment, enhancing the adaptability of farmers and their ability to respond to changes and to exploit opportunities.
Altieri, Miguel A. 1989. Agroecology: the Scientific Basis of Alternative Agriculture, Westview Press, Boulder and IT Publications, London.
Boserup, Ester. 1965. The Conditions of Agricultural Growth: the Economics of Agrarian Change Under Population Pressure. George Allen and Unwin, London.
Chambers, Robert and Leach, Melissa. 1989. Trees to Meet Contingencies: savings and security for the rural poor. World Development 17 (3), 329-432.
Gupta, Anil K. 1989. Scientists' views of farmers' practices in India: barriers to effective interaction. In Chambers, Pacey and Thrupp (eds). Farmer First, pp 24-31.
Harrison, Paul. 1987. The Greening of Africa: Breaking through in the Battle for Lar~d and Food. Paladin Grafton Books, London.
lIED. 1989. Patchy Resources in African Drylands: a review of the literature and an agenda for future research and development. A proposal of the Drylands Programme, lIED, London.
Juma, Calestous. 1987. Ecological complexity and agricultural innovation: the use of indigenous genetic resources in Bungoma, Kenya. Paper for the Workshop on Farmers and Agricultural Research: Complementary Methods, IDS 26-31 July, cited in Chambers, Pacey and Thrupp (eds). Farmer First, pp. 32-34.
Kolarkar, AS., Murthy, K.N.K. and Singh, N. 1983. Khadin - A method of harvesting water for agriculture in the Thar Desert, Journal of Arid Environments 6, 59-66.
Pacey, Arnold and Cullis, Adrian. 1986. Rainwater Harvesting: the Collection of Rainfall and Runoff in Rural Areas. Intermediate Technology Publications, London.
Richards, Paul. 1985. Indigenous Agricultural Revolution: Ecology and Food Production in West Africa. Hutchinson, London.
Scoones, Ian. 1988. Patch use by cattle in a dryland environment: farmer knowledge and ecological theory. Paper for the workshop of Socioeconomic Determinants of Livestock Production in Zimbabwe's Communal Areas, Mazvingo, Zimbabwe. Centre for Applied Social Science, University of Zimbabwe.
Wilken, Gene C. 1987. Good Farmers: Mexico and Central America. University London. Traditional Agricultural Resource Management in of California Press, Berkeley, Los Angeles and London.
About the Author
Prof. Robert Chambers is an internationally renowned author of books on participatory community development, a champion of participatory methodologies such as Rapid Rural Appraisal (RRA) and PRA (Participatory Rural Appraisal) and a scholar with extensive experience on development in South Asia. He is affiliated with the Institute of Development Studies at the University of Sussex, UK. He can be reached by e-mail at R.Chambers@ids.ac.uk.
This article was excerpted from the original published as _Microclimates Unobserved_ in the Gatekeeper Series (No. 22) by the International Institute for Environment and Development (IIED).
For more information on the Gatekeeper Series or to purchase the original booklet, contact International Institute for Environment and Development (IIED), 3 Endsleigh Street, London WC1H ODD, United Kingdom; Tel: +44 (0)207 388 2117; or visit http://www.iied.org and go to the online bookshop.
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