Why
are
non-engineered or owner-built structures more vulnerable to hazards?

Non-engineered/owner-build structures are more vulnerable because they can be poorly built. Without proper knowledge to build the right structure, the structure is more at risk of abnormalities or destruction from hazards such as rain, hail, strong winds, and debris.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.

yes it is weird but true