The earth as a whole is roughly a closed system, but "usable water" is not. Most resource problems are not about the quantity of some thing changing as a perce

The earth as a whole is roughly a closed system, but "usable water" is not. Most resource problems are not about the quantity of some thing changing as a percentage of earth's matter. Most resources are about density and composition. If all of the (non-ice) freshwater on earth was suddenly dumped into the ocean, we'd have the same amount of overall water - but little to no drinkable water. Likewise, we're not really creating new carbon by burning fossil fuels. We're moving and re-distributing it. Compared to being deep underground, the form we create by burning captures much more heat, causing many problems.