(a)(i) Conservation: Planned/wise/judicious use/management of the earth's natural resources; in order to ensure sustenance/availability/continuity; and preservation of the quality of the natural/original nature of the environment.
(ii) Factors responsible for decline of abundance and variety of wildlife:

Commercial hunting which kills off animals indiscriminately
industrialization which involves clearing of forests
for various purposes/construction/farming/urbanization
destruction of habitats of wildlife by human activities
bush burning/noise pollution leads to wildlife migration
environmental pollution which releases dangerous materials that degrades environment making it unbearable for the wildlife
massive/excessive tree felling to make charcoal/domestic uses
lack of awareness/inadequate education of populace on the need for conservation
lack of adequate funding to enforce conservation policy.

(b) Ways by which the Government can improve the situation:

establishment of forestry departments
establishment of Environment Protection Agency to improve the situation
creation of Parks and Games Reserves/any correctly named example; to preserve/maintain plants and animals in their natural environment
conservation education carried out through tree planting! campaigns against bush burning/ tree felling /poaching
conservation laws to regulate tree felling; poaching/hunting of wild animals and bush burning
establishment of zoological gardens preserving endangered species.

(c)(i) Eutrophication: Excessive growth of plant life/algae/algal bloom; in water courses/bodies, caused by an increase in organic nutrients and minerals; leading to the death of aquatic organisms.
(ii) Causes of eutrophication: Overuse of fertilisers/plant nutrients which drain off into water bodies; sewage discharge; was from fish farming.