The exploitation of this bioproductivty trade human niche (market opportunity: northern nigeria. Still arid, but more water and biomass such as cattle. Markets are ecologically significant elements: trade links are important parts of an ecosystem. Markets allow for specialization and thus become (human) ecological niches. International markets may displace people and local markets, however. Ecological balance is needed: south east africa. Human innovations from river bed irrigation system. Skills help us survive but it depends on what kind of envr we live in- we adapt only through culture, we are genetically inept: cameroon. Low density of people due to rapid evolution and succession of organisms (unproductive soils, unpredictable and dangerous organisms) Slash and burn (swidden) cultivation can actually be sustainable processes. Vegetation cut down, organic material is left to decompose, and sunlight can reach the ground for crops to grow. Secondary succession can be used to recolonize the site.