(a) Conservation of natural resources is necessary for the following reasons:
(1) The wise use/safe-keeping/ management of natural resources, for the benefit of mankind, (2) To ensure their continuous availability/avoid their decline/extinction.
(b)(i) The following are the methods of soil conservation:
(1) Planting grasses/legumes
(2) Crops must be planted on ridges across slopes
(3) Practicing shifting cultivation/bush fallowing/crop rotation
(4) Avoiding/preventing bush burning
(5) Addition of manure/fertilizer to the top soil
(6) Spreading a layer of vegetable material on cultivated farmland/mulching
(7) Constructing ridges across the slope of the land at intervals/contour ridging
(8) Planting trees/reafforestation
(9) Prevention of over-grazing
(ii) Natural resources that can be conserved are:
(1) Water
(2) Forest
(3) Wildlife
(4) Mineral resources
(5) Genetic mineral/genes
(6) Petroleum/coal/gas/fossil fuel/ iron ore, tin, gold
(c) Factors that negatively affect conservation of forest in West Africa include the following:
(1) Uncontrolled/over-exploitation of forest trees/indiscriminate felling/lumbering of forest trees
(2) Lack of afforestation/tree planting.
(3)Bush burning/wild fires
(4) Non enforcement of conservation laws
(5) Lack of /no knowledge of conservation education/awareness
(6) Use of firewood/charcoal for fuel
(7) Air/soil pollution.
(d) Denitrification stage of the nitrogen cycle: -

Denitrifying bacteria/certain fungi in the soil
Convert nitrates into nitrites
Some bacteria/pseudomonas spp can convert ammonia/nitrite/nitrate into gaseous nitrogen, which is released into the atmosphere, leading to reduction of soil nitrogen content, resulting in reduced soil fertility