Biomes are specific to an areas climate. E.g. species of trees in rainforests won't be in temperate conditions. If the climate were to change then the organisms in the biome wouldn't be adapted to the new conditions causing a negative impact, e.g. if a rainforest became drier then there would be less water available for plants. Also organisms will migrate to another area which is changing to their adapted conditions e.g. temperate organisms in the northern hemisphere will migrate further north as areas warm up because their current location is too warm but colder regions further north are warming up and becoming more suitable for them.
Would wait for a A2 geography student to answer this question before taking mine as they'll be able to give a better answer.