Fungal mycorrhizae, which grow connected to the root systems of many plants, greatly increase root surface area and the plants' ability to collect nutrients. Certain orchids are among the higher plants that require unique mycorrhizae to flourish. Finally, lower plants play a critical role in recycling water. Mosses, for example, act like sponges absorbing large amounts of rainfall that would otherwise soak into the ground or run off into streams and rivers. Later, when the air humidity drops, mosses release the stored water and re-humidify the air.
Loss of habitat is a major threat to mosses, lichens, fungi and algae.
In harvesting a forest, we not only remove trees but also strip away many lower plants. Scientists have found that non-vascular plants tend to recover slowly leaving fewer species after a disturbance. Over-collection is also a serious threat to many lower plants. Lichens and mosses are collected for use in the floral trade. Moss is used extensively as decoration and as a moist packing material for delicate roots of commercial plants.