1. Changes that are beneficial :
(a) Growing of plants into trees.
(b) Change in season after specific interval of time.
(c) Ripening of fruits.
(d) Cooking of food into eatable dishes.
(e) Migration of birds form one place to another.
2. Changes that are harmful :
(a) Burning of coal,plastic,wood and other substances that release CO,SO2.
(b) Cutting of trees leading into soil erosion,fall in O2 levels in air etc.
(c) Contamination of rivers.
(d) Urbanisation leading to disappearance of forests.
(e) Growth in population,leading to non-judicious usage of natural resources.