> How do you propose we protect the landscape, water, ecology?
Through environmental regulation, protected areas, permitting, environmental reviews, etc. This is the common model in most of the world. It works well in some places and not well in others, just as laws sometimes work, and sometimes don't.
Passing subsidies to farmers might (strong emphasis on might) have some unintended benefits to the environment (or not), but it is a terrible way to try to protect the environment, particularly because most (if not all) of the investment in this goes to the profit margins of the farmers.
And sure, there are plenty of real world examples: look at environmental review and permitting processes for your city or state. I happen to be very close to a number of environmental engineers who handle such permits on a daily basis, both on the granting as well as on the requesting side.
Want to build a road on your farm, or increase your farming area? You'll likely have to submit a permit to Fish & Wildlife, as well as to the county water authority, to the Army Corps of Engineers, etc. Depending on the type of work, you might need to hire an engineering firm to do hydrological analysis and understand how the work impacts water drainage and flow, how it impacts flow downstream to other properties, and often enough to sensitive environments miles away.
One example was a friend of mine doing work for a homeowner in an unincorporated area who wanted to build a culvert under their driveway to increase drainage and reduce the risk of flood on his property.
Well, while building the culvert would increase the flow and decrease the risk of flood in his property, it would also mean that the flow downstream would increase significantly, resulting in higher flood risk to other properties downstream. Open, rugged soil acts as a sponge and as "potential energy dissipators", slowing the flow of water during heavy rains. Paving means that all the water flows downstream quickly, flooding lower areas.
Also, the culvert would channelize a lot of the water flow, meaning that the toxic substances from the driveaway and the home's roof would not be spread out in a harmless way (the solution to pollution is dilution) that can be handled by the ecosystem, bubt would flow quickly to streams and pools in the lower areas, increasing the concentration of such substances to unacceptable levels and damaging the critical environment for an at-risk endemic species of frogs.
While the homeowner dismissed my friend's concerns and decided to request the permit anyway, it is highly likely that the permit will be rejected because of the points above (actually, I know the person handling the permit on the government's side, it will be rejected for sure).