It is best to say that the protection to properties offered by sea walls along coasts

a. decreases the present and future risk to human properties.

Explanation:

According to a different source, these are the options that come with this question:

a. decreases the present and future risk to human properties.

b. increases both the present and future risk to human properties.

c. decreases the present but increases the future risk.

d. increases the present but decreases the future risk.

A sea wall is a form of defense that is usually built in places were the sea impacts directly upon the landforms of the coast. Because of this, such walls anc be useful in areas that are particularly close to the water. Sea walls usually protect areas of human habitation, conservation and leisure activities. However, these can have negative environmental effects, as they impede the exchange of sediment between the land and the sea.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.