Plants are subject to a number of natural dangers through disease, adverse weather and insect depredations; man-made disasters such as pollution and excessively rapid development take their toll as well. The preservation of plant species and plant genetic diversity is a matter of scientific principle or aesthetics to some, others recognize plants as nature's pharmacy and plant-derived medicines continue to be discovered. Some plants belong in very important ecological chains, and without being crops themselves, their absence would affect such important natural activities as pollination, insect reduction by birds and soil conditioning.
Vegetation can include the edible, the medicinal, the ornamental and also, from the anthropocentric viewpoint, the economic: that which provides wood, fibre and chemicals. Vegetation that is non-edible is also essential for crop production to prevent erosion, provide wind-breaks or shade, or to mulch or condition the soil. Vegetation provides oxygen for the planet. Without vegetation most of organic life would die, and from nature's point of view (perhaps less biased than man's) the vegetable kingdom is therefore not deemed inferior to the animal. In scientific classification, vegetation is one of the three kingdoms, the others being the animal and the mineral. All three share the tendency to deteriorate with age and to be subject to environmental influence. The hazards which animals and plants share include: adverse weather, disease, old age, genetic accidents and even plant war. Like the smallest organisms, the largest and most intelligent plants are involved in the struggle for life among themselves and are the natural prey of the animal kingdom. On the other hand, plants have their defences and there are even plant predators.