Like we need more water in the UK
I understand your point, but the UK is one of the biggest wasters of resources and energy, we could do more and it can only benefit us anyway with the saving in money and less going to landfill.
But the transfer of water from a country that barely has any to one that has plenty is a problem, for example a lot of our cherry tomatoes come from Morocco where they are going ever deeper into their water table, that water table is not being replenished and local farmers producing food for the local population are starting to have problems, i wonder how many of us have thrown away those same cherry tomatoes (that's just one small example). Many other countries are experiencing desertification through large scale clearance of forests and river diversions for agriculture. All this affects local climates and habitat that has a knock on effect for the rest of us.
Another example, this is the result of rivers being diverted for agricultural projects. The Aral sea was once the 4th largest lake in the world, it was 3.5 times larger than Wales! Many of our clothes would have been made from cotton produced here.
The large scale clearance of the Amazon forest to produce cheap meat for the fast food chains has had several impacts. The cleared area quickly becomes unproductive and what is left is baron land. There is so much still to discover in that great forest not only in terms of wildlife but chemical compounds found in diverse plant material that have many medical uses. We are fast loosing this and its humanity that looses not just Brazil.
Less we forget, 60million people is a lot for a little island, and without the produce of much poorer countries with corrupt governments and very cheap labour we could not possibly support our population as the cost of living would dramatically increase. I wouldn't like to work for $1 a day but someone has to so that the richer countries can consume.