Maybe you do but, as I've just written, I do not understand his pointI think simonh2 made my point rather well
I don't doubt it, but you are again back to the circumstantial evidence relating to the chronological changes in the atmosphere and the burning of fossil fuels.Well we know from the ice record the contribution of just plants, and it shows a marked difference prior to the burning of fossil fuels
I'm not sure how one could ascertain that since it is so confounded with other things. How was this evidence obtained?It could, but evidence I have seen suggests global photosynthesis is on the rise, and has been for the past 200 years.
I wasn't necessarily suggesting that the toxins had to be recognised herbicides. I was merely illustrating that chemical substances have the potential to interfere with photosynthesis. In any event, even if the chemical is 'broken down quite quickly', if it is constantly fed into the environment, it will always be present in levels potentially high enough to have an effect. The water in the water tank in your house is 'used up quite quickly' but, because it is constantly being replenished, the tank will nearly always be nearly full!Most herbicides don't linger in the ecosystem and are broken down quite quickly.
Kind Regards, John