The distribution of a species is where it lives. Each species can survive and reproduce only within a certain range of conditions, so as the climate changes, the areas with suitable conditions move.With global warming:
• species move towards the poles and to higher altitudes, following the cooler conditions they need. Many British butterflies and birds, such as the comma butterfly, have spread northwards;
• species at the cold limit of their range, such as those on mountain tops or in the Arctic, have nowhere left to go and may die out locally. Polar bears, for example, depend on sea ice to hunt seals;
• species from warmer climates move into new areas, where they may compete with, prey on or spread disease to native species;
• pests and disease vectors spread. Mosquitoes that carry malaria and dengue can survive further from the equator, and insect pests can complete more generations a year.Timing matters too. If warming makes a plant flower or a caterpillar emerge earlier, but a bird that feeds on it does not change its breeding date, the two get out of step. This mismatch reduces the food available for the young and can cause bird populations to fall.Species can only shift their range if they can disperse quickly enough and if suitable habitat exists. Habitat fragmentation by farms, roads and towns blocks movement, so slow-moving species and those in isolated reserves are most at risk. Some species may adapt by natural selection, but this is slow compared with the rate of climate change.
• species move towards the poles and to higher altitudes, following the cooler conditions they need. Many British butterflies and birds, such as the comma butterfly, have spread northwards;
• species at the cold limit of their range, such as those on mountain tops or in the Arctic, have nowhere left to go and may die out locally. Polar bears, for example, depend on sea ice to hunt seals;
• species from warmer climates move into new areas, where they may compete with, prey on or spread disease to native species;
• pests and disease vectors spread. Mosquitoes that carry malaria and dengue can survive further from the equator, and insect pests can complete more generations a year.Timing matters too. If warming makes a plant flower or a caterpillar emerge earlier, but a bird that feeds on it does not change its breeding date, the two get out of step. This mismatch reduces the food available for the young and can cause bird populations to fall.Species can only shift their range if they can disperse quickly enough and if suitable habitat exists. Habitat fragmentation by farms, roads and towns blocks movement, so slow-moving species and those in isolated reserves are most at risk. Some species may adapt by natural selection, but this is slow compared with the rate of climate change.