Question

How is the pH altered in an ecosystem? (Both terrestrial and aquatic)

Answer 1

The pH of a substance refers to the degree of acidity or alkalinity of that substance, that is, pH is a measure of how acidic or basic a substance is. The pH scale ranges from 0 to 14. Point 1 [very acidic] to 6 [slightly acidic] is considered to be acidic while point 8 [very basic] to point 14 [slightly basic] is considered to be basic. Point 7 is neutral. 
In an ecosystem, the pH of the terrestrial or the aquatic environment can be altered by pollution such as mining erosion, radioactive materials, oil spillage, excess nutrients, etc.

Answer 2

The pH of an ecosystem can be altered by the injection of a foreign matter with a different pH. An example of this is acid rain; rain with a lower pH falls on an ecosystem, lowering the pH of the soil such that plants begin to wither. Acid rain will also lower the pH of streams and other water bodies with similar decrease in productivity.