Not only will the warmth improve yields from cold lands and the rainfall improve yields from some dry lands, but the increased carbon dioxide will itself enhance yields, especially in dry areas. Wheat, for example, grows 15–40 per cent faster in 600 parts per million of carbon dioxide than it does in 295 ppm. (Glasshouses often use air enriched in carbon dioxide to 1,000 ppm to enhance plant growth rates.) This effect, together with greater rainfall and new techniques, means that less habitat will probably be lost to farming in a warmer world. Indeed under the warmest scenario, much land could
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