I met grape farmers on holiday to france, that used to spray twice the normal amount of bordaux mixture on the grapes near the roads. Since it made the plants look blue. And this detered people riding on the roads from stealing their grapes.
They saw large differences in both quality and quantity of their dubble sprayed grapes compared to single dose sprayed grapes. He also commented soil life was almost absent near the dubble sprayed grapes. grapes where in culture there for around 40 years i think.
I do not know of area’s that are abondoned just because of copper toxicity. Not because copper is not toxic. But because where copper levels are so high to be immediatly toxic. Things have gone so horrible wrong that other heavy metals and toxic substances are also present.
The thing with copper as with many heavy metals is that it won’t deal measurable damage to you today. But small amounts for a really long time. And since it stays toxic for so long, it tends to build up.
Usualy it damages soil life first. (but also for a really long time into the future) But the effects of less soil life aren’t immediatly noticeble. Then if it builds up to higher levels it becomes phytotoxic to certain crops (legumes, grapes , cereals and also quite a few leafy vegtables) And then our land use tends to switch to searching for another spot, or to a more tolerant species. Or we just learn to deal with a lower yield.
So copper tends not to lead to complete abondonment but more to sustained lower yield. Less visable but still really inportant.
Also the oldest mention of copper pesticide/fungicide use i could find was 150 years ago. And use then was really limited. Most places have had “modern” use for a relativly short time (around 50 years).
That is not enough for the buildup to lead to extreem cases like abandonment. But again immediate toxicity is not the main problem. It is more lower yield and toxicity over longer timeframes. Consider a 10% yield loss, that lasts for 1000 years. That has pretty extreme consequences. But loosing 10% yield today versus 50 years ago. It will be hard to spot/remember the difference. It’s less visible but still there.
Also drawing the line of not using a toxine only if it leads to complete abandonment of an area is an pretty extreme thing. I would personaly consider using less or not using something long before it would lead to chernobel like consequences.
I don’t completly follow you here. You could use the logic above to also justify spinkeling uranium over your cereal. The uranium is somewhere on our planet. We can only move it. It always has to be someplace on this earth. Might as well be in your cereal?
The thing is, copper that is sequestered deep into the earth or for example in copper electronics. Does not come into contact with plants or our food. So has no immediate danger in that case. However if you powder it up, disolve it and than spray it on food plants and food growing soil. Your taking somthing that was sequestered away from food(production) and introducing it to the food production system.
Excess copper concentrations are recognized as having phytotoxic
effects on the growth and development of most plant species,
usually apparent in the form of chloroses and a reduction in total
plant biomass. Some crops – including legumes, grapes, hops, and
cereals – are particularly sensitive to high copper levels.
The deleterious effects of excessive copper on soil microbes are
well established, as is copper’s toxicity for some groups of soil
fauna
Quoted from
https://www.mdpi.com/2071-1050/11/22/6215/pdf
If you read scientific or university or certification/agricultural institution documents. I notice that they don’t talk about if they will replace copper. But about how and when they will. And what alternative is most promising.
Some countries that export a lot of fruit that benefits from copper sprays. Have outright banned copper use. Or reduced the maximum allouwed to spray (france for example). Not to tank their own fruitgrowing economy. But to make it more future proof. Think of france, copper is really inportant for grape production (powdery mildew). But still they are trying to use less and search really hard for alternatives. In both organic and non organic culture.
Notice though that im nowhere advertising a copper ban in any of my posts. I am just advertising responsible use. And to be aware of the cost benefit choice you can make!
-if lime sulfur works good enough, don’t use copper.
-use the minimum amount needed.
-don’t mix more then you need.
-Spray when no rains are forecasted.
-Don’t spray leftover solution, just because it is left over. If you sprayed enough it’s enough. At that point less=more.
-Don’t dump exces spray solution.
i notice this discusion is draining my energy a bit. So i’ll probably leave it at this.
I would love it. If people asked for proof somthing did no harm/ was not toxic. Instead of asking for others to “prove” that somthing is toxic.
In the end it is your choice to make. And id hope youd value your health and that of the people after you and that of the planet. But the choice is yours, not mine to make.
so is the responsibility of that choice, in both searching for safety information and the consequences of the choice you make.
Edit: those last few sentences are not specificly aimed at any person(s) in this discusion. But more a general thought. I am sometimes dissapointed at how easily people/industry/governments use things without considering long term safety. And then only take action when a problem arrives. I like a more proactive “looking ahead” approach myself. I just want to say copper is not extreemly bad. And i won’t think less of anyone using it!! Nothing personal 
I just would like you to consider using it responsibly.