The danger I see is that the real wacko environmentalists will use what he says on the one hand about depletion of resources and use it to beat the Church over the head about population control, abortion, euthanasia, and so forth.
I will have to look up Julian Simon, but I've argued with other Catholics that surely a God who was smart enough to give us the Sacrament of Reconciliation when we pollute our souls would also account for environmental pollution.
I'm not sure I would even recommend reading "Laudato Si'". It's too long by half and not well organized. It's possible to use your time reading something better...
God save Pope Francis!
God save the Catholic Church!