(a)if we go on cutting trees :
then the temperature will increase to greater extent because there will be an instant rise in the level if CO2 which will in turn trap more sunlight, thus increasing the atmospheric temperature leading to global warming. Global warming will cause melting of glaciers which will rise the water level. Increase in the level of green house gases will cause severe respiratory diseases and skin cancer.
(b)if the habitat of an animal is disturbed :
then the animals will lose their natural habitat and will start becoming endangered. They will move to another place in search of food, water, shelter and protection which in turn will cause ecological imbalance in that particular area.
(c)if the the top layer of soil is exposed :
then the exposed layer will lose all its nutrients, especially the humus which is the organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms. The water holding capacity of soil will gradually decrease due to lack of soil nutrients.