Water Vulnerability

So we've looked at how the human population affects (and has in the past affected) green house gas concentrations and biodiversity (animals and plants). Now I want to take a quick look at our effect on water, so here's a brief summary of Vörösmarty et al.'s (2000) article where they look at how climate change and population growth affect water stress.

They point out that a lot of focus has been on how global warming contributes to water vulnerability whereas actually direct human impact (i.e. consumption) is a lot more important than we think. They emphasise that future water demand will be based on population growth, economic development and projected changes in water use efficiency and what they find, which I think is interesting, is that water use per capita is expected to decline. So although there will be increased water stress that won't be due to an intensification of use, it will be down to population growth, migration, and development. Couple this with the fact that most of the world's population growth will now take place in cities, and you get all the issues around pollution and water-borne diseases. 

What they also determine (which you can see in the maps below) is that not only is a large portion of the world under water stress (I don't think it's the first time we've heard that though), but rising water demands are more important than greenhouse warming in "defining the state of the global water system until 2025" (p.1). You can see below: (without getting into too much complication), the fact that there is more red colour in the middle diagram than in the first means that population change has more of an effect than simply climate change on water demand and use. Obviously when the two are combined they have the biggest effect. And as climate change gets more significant as time goes on, this effect on water stress will get worse and worse and (judging by what the authors said) I'm assuming climate change may even overtake population change as having the most significant effect (as either population growth is slowing, or the lag between human activities and climate change comes into effect).

Anyhow, it is clear that humans and the growth of the human population are having effects on water vulnerability – directly through use and demand; and indirectly through causing environmental change.

  

source: Vörösmarty et al. (2000)