[bruce511]

I don't think we need worry too much about desert habitats being removed. Deserts are large (and getting larger) and the amount of land which could realistically benefit from desalination is a tiny fraction of that.

While brine can impact local salinity, so does treated-effluent outflows (mixed together they are neutral.) Regardless elevated brine levels drop off sharply from the point of outflow.

[ehnto]

We are really good at mis-estimating scale. So we know brine decreases sharply from the point of outflow, but do we know what 50 years of brine outflow at tens of thousands of locations around the world would do?

If it's profitable, it'll be implemented all over, and underestimating that cumulative effect is something we would plead willful ignorance on as we have done with other industries in the past.

Second point I will try to make, habitats are often unique and small, we would just want to make sure an ecosystem is truly ubiquitous before destroying a small pocket of ecosystem.

Especially now, there are animals that live in just one or few specific spots. We should be careful.

[tzs]

I'd expect that long term the brine would do bad things near the places it is released but would not have any noticeable long term consequences much farther away as long as we don't discharge it somewhere where it destroys something local that turns out to be a dependency of something far away.

That's because almost all the water that is taken out of the ocean will make its way back to the ocean. We just borrow it for a while.

If all the water used by humans were taken from the ocean, we'd take about 1/300000th of the ocean's water per year. Most of that will be back in the ocean within 200 years. That puts the cap on the amount of water that would be missing from the ocean of 1/1500th of its volume, which means that the steady state increase in salt concentration would be less than 0.1%, which is much less than the natural variation in ocean salt levels.

[jdjdjsgwiwj]

With all the talk of rising oceans... Taking some sea water out might be a good thing ;)