Whale watching is the practice of observing whales and dolphins (cetaceans) in their natural habitat. Whales are watched most commonly for recreation (cf. birdwatching) but the activity can also serve scientific or educational purposes. A 2009 study, prepared for IFAW, estimated that 13 million people went whale watching globally in 2008. Whale watching generated $2.1 billion per annum in tourism revenue worldwide, employing around 13,000 workers. The size and rapid growth of the industry has led to complex and continuing debates with the whaling industry about the best use of whales as a natural resource.