From a biologist perspective tropical forests are the richest and most exciting areas on earth sheltering a diverse wildlife. Tropical forests are differentiated from other type of forests due to their gigantic trees amazingly diverse fauna of colorful birds, millions of brightly hued insects, and a variety of fascinating mammals. It is widely accepted that tropical lowland forests are the most species-rich type of terrestrial ecosystem (DeVries & Walla, 2001; Bush & Lovejoy, 2007), for example, a hectare of Malaysian tropical rainforest may contain 180 kinds of trees.
Tropical rainforests are generally concentrated near the equator in Asia, Africa, South America, Central America, and on many of the Pacific Islands. According to WWF's biome classification, tropical rain forests are considered a type of tropical wet forest and may also be referred to as lowland equatorial evergreen rain forests. All five layers of tropical rainforests i.e. emergent layer, canopy layer, understory layer, shrub layer, and forest floor are enriched with different plants and animals.
Tropical deforestation, desertification, decreasing biodiversity, climate change and the scarcity of fresh water are issues of recent and ongoing global conflict and debate (Matti Palo and Jussi Uusivuori, 1999; Matti Palo and Heidi Vanhanen, 2000).
On the other hand, according to various studies by WWF committees, rainforests are the most endangered habitat on earth and every year approximately 140,000 sq km of tropical rainforests are destroyed because of small scale agricultural practices and timber industry. The rate at which these forests are disappearing is again fueled by the rapid population growth in the areas harboring theses forests.
Small-scale agricultural practices
Generally used definitions of shifting cultivation defines it as a agricultural system where plots of forests land are cultivated temporarily by clearing the land by the means of fire or logging and then abandoned when the soil looses its fertility. When the fertility level of land drops below economical viability, it is left to be reclaimed by natural vegetation. The ecological impacts of shifting cultivation are often devastating.
With the development of a holistic view of agro-ecosystem approach and agriculture being considered as a part of a greater natural ecosystem, the shifting cultivation is defined from a different perspective. Whereas many earlier studies described the shifting cultivation system as inherently stable and provided a checklist of attributes, more recent work based on an agro-ecosystem approach has stressed fallow as part of an overall subsistence strategy, flexibly responding to stress as the social, economic or natural environments change (Warner, 1991; Gliessman 1985, Altieri et al 1973).
The term agroforestry is used for a combination of agriculture and forestry technologies for creating a more integrated, diverse, productive, profitable, healthy and sustainable land-use system (National Agroforestry Center, NAC). According to the World Agroforestry Centre (ICRAF), "Agroforestry is a collective name for land use systems and practices in which woody perennials are deliberately integrated with crops and/or animals on the same land management unit. The integration can be either in a spatial mixture or in a temporal sequence. There are