They were classified as criminal tribes because they use to move from place to place with their herds . The colonial government thought that it destroyes and kills the young saplings and prevents growing of new tress. They also thought that although they raise their animals but it causes no use to nature but disturbes the balance of nature.
this is the reason why they were classified as criminal tribes by the colonism government.
But it was not true as when their animals used to move from place to place , the pollen grains gets stick on their bodies and it fells on the separate land and it encourages growth of new plants.. even due to their movement , the soil gets ploughed out and when the rain comes .. it is easily absorbed by the plants...
Hope it helped you..
thanx for giving time to read my answer..