This will destroy the near shore ecosystem, because desalination dumps brine that kills everything, while at the same time destroying the desert ecosystem because it gets converted into something local flora and fauna can no longer live in.
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.
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.
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.
The brine levels can be greatly reduced by pumping more water to dilute the brine. RO desal projects tend to optimize for an energy efficient local optima that targets minimum energy subject to maintenance constraints. But if energy is nearly free you can instead pump a lot of extra water to solve the issue by moving more volume over more area further from shore.
1) cheaper energy means you can mix more water in to get whatever salt level you want.
2) you can mix in the output of your sewage plants
3) most water is borrowed and returned, not a huge net loss. Every toilet full returns to the ocean, every washing machine run, etc.
Solar powered desalination doesn't make the list for things to worry about over the next 100 years.
>This will destroy the near shore ecosystem, because desalination dumps brine that kills everything,
WRONG
WRONG!!!
No, we used the brines to create even more batries which store our solar charge
Now we have POWER at day and at NIGHT. 24/7. 247 we are producing the brines, but then that goes onto make more batries. Ain't no ecosystem destroyed here (though I'm sure people will try to perform a regression of muh bad event unto muh new technology because that is a timelessly vogue thing to do)
