Grasslands as the term states, are lands covered with grasses. The Grasslands Biome, sometimes includes savannah (grassland with a few trees spread throughout), but if you look at the grasslands that are comprised almost entirely of grasses without taller, woody vegetation, then the area covered by such grassy areas on the
world map becomes much smaller. The existence of grasslands, is dependent upon several factors or variables. The foremost of these is a climate with limited precipitation, too much for desert, but too little for larger more woody plants. This is of course an over simplification. The
Holdridge Life Zones assigns the placement of these plant communities as being determined by the amount of precipitation in relationship to the amount of evapotranspiration--or a water budget for biomes.
The Holdridge Life Zone chart shows a relationship between temperature, and precipitation, in relationship to plant communities or "life zones".
Grasslands evolved with the grazers that feed on them. The bison have been all but completely replaced by beef cattle. Where a diversity of plants once flourished, we now have the breadbasket of America, and much of the world . Fields of wheat, amber waves of grain, now feed us. What has not been farmed has been further impacted and reduced by progress, housing developments and strip malls. The vast tall grass prairies that the pioneers crossed in covered wagons is now a thing of the past, replaced by the view of monsterous green harvesting machines.
Much depends on the success of this agriculture, and as we have become more dependent on just a few species to feed the world's 6 Billion people, the question of climate, and of
our ability to make rice, wheat and maize supply food for most of us is no small concern. When we convert huge chunks of a species rich landscape, to one species--to a monoculture, we've drastically impacted biodiversity, food is of course a necessary evil, though grain for fuel production seems a little dubious.
