Temperatures on land and sea, and especially changes within these temperatures, can affect what species eat by making it more difficult for plants and animals to survive. So if a certain animal eats a certain type of plant, and that plant can only survive in a certain temperature range, that animal will lose a source of food if temperature changes make it more difficult for that plant to survive. To cite a specific example involving the sea, many scientists have suggested that certain sea birds, whales, and fish will be harmed by rising marine temperatures. This is because their food supplies, such as krill and some fish, which are adapted to cooler waters, will begin to move north and south in search of these waters. To put it another way, as the cooler zones within the ocean shrink, the number of species that they can support decline. They will have to find new food sources or risk extinction.