Acid rain greatly alters the nutrient content of the soil. Due to acid rain, important minerals such as calcium, potassium and magnesium leach out from the soil, rendering it unfit for crops. For example, calcium leached out from the soil due to needles of red spruce causes trees to become less tolerant to cold and exhibit winter injury or even death. Acid rain also increases the acidity of the soil due to which large areas of crops are adversely affected. Forests located on high altitudes are affected greatly as they are often surrounded by clouds and fog, which are more acidic than acid rain.