After flowering plants and ferns, mosses are the most diverse group of plants, with more than 10,000 species. This makes mosses almost twice as diverse as mammals. Mosses don't receive as much attention from us as flowering plants, ferns, or conifers because most mosses are small and inconspicuous. They have no vascular tissue or wood to lend them structural support, nor do they have large leaves or showy cones or flowers. Mosses play important roles in reducing erosion along streams, water and nutrient cycling in tropical forests, and insulating the artic permafrost.