Re: how does the water cycle help the carbon cycle?

Felipe,

The water cycle and the carbon cycle are not the same, because water and carbon are not the same. However, water and carbon are often found in the same places, and involved in the same processes.

Consider the principal processes that make up the carbon cycle: plant growth, plant and animal decay, ocean uptake, and fossil fuel burning. For a good picture of these, see
http://www.windows.ucar.edu/tour/link=/earth/climate/images/carboncycle_jpg_imag e.html

Water is closely involved in many of these processes. Plant growth through photosynthesis, for instance, removes carbon from the atmosphere by exchanging it with water: without water, plants cannot absorb carbon and grow. Decay is also extremely slow when water is limited. The water cycle (you can find a nice diagram here: http://ga.water.usgs.gov/edu/watercyclesummary.html) supplies the water necessary to keep the carbon cycle moving. The step called "evapotranspiration" in the diagram is where plants release water into the atmosphere, which they must do to absorb carbon and grow. This diagram makes it look like rain only happens in the mountains, which of course is not true: most rainfall on Earth falls directly back into the oceans.

If carbon cycle processes like photosynthesis and decay stopped, the water cycle would still continue, though its balance might be upset. But if the water ceased to evaporate off of the oceans and rain down on the land, the carbon cycle would not be able to function. Human survival on the Earth is dependent on both systems.

Hope this helps,

Edward J. Hyer, Ph.D.