Agriculture forms the basis of settled communities and civilization itself. Not all plants need direct sunlight to survive. Fungi get nourishment from other green plants or from dead matter on the ground. Some, like the starfish fungus, can grow in strange and unexpected ways, but they still need to disperse their seed, just like any other plant. Of all the plant forms on Earth, none is more valuable than the many different forms of tree. Conifers among the largest plants in the world, bear cones instead of flowers. Coniferous forests are cultivated extensively. Flowering or deciduous trees once covered much of the Earth 's surface. Through the centuries, these great forests have been cleared to make way for settlement agriculture and later for industry. Continued destruction of the remaining areas of forest. Alters permanently the delicate relationship between plant life, climate and the Earth itself. They create a rich resource of food and shelter, essential for the continued survival of all life on earth, whether humans, animals.