The truth is that tourism has also its negative side mainly for the host community. The environmental impact caused by your travelling might be minor, but think about the total impact by all visitors.
Greenhouse gases released from plane during your flights, carbon emissions caused by your local transportation by car or bus, electrical consumption during your stay in the hotel are just some of all the factors that contribute to the total carbon emissions during your holidays. What we all should try to do is to offset those emissions. A carbon offset is a reduction in emissions of carbon dioxide or greenhouse gases made in order to compensate for or to offset an emission made elsewhere.
Most airlines have started being very sensitive about this matter. They give you the chance to offer an amount for offsetting carbon emissions caused by your flight. Choose those airlines for your travel.