You might check with a real estate lawyer; it would be highly unusual for a restriction in a deed or contract to pass to the next owner in perpetuity. I suspect the "no development" restriction would be voluntary, enforced by contract, for a limited time. This is an old common law restriction, called "The Rule Against Perpetuities", which was implemented to keep land from being under control of one family forever. Just a thought.
en.wikipedia.org
Actually, conservation easements can run in perpetuity. That's the point of many of them, rather than going with a simple deed restriction. How they get around the perpetuity concerns is by stripping off certain rights to the land and having them held by some other entity, such as a Land Trust or the sate or some other governmental agency (the Vt Dept of Fish & Wildlife holds some easements here, for example.)
With a conservation easement, you are basically granting some of the rights associated with that land to another entity. It works much like an access easement might give your neighbor the right to build a driveway across your land to access their property, or a utility easement gives the power company the right to build and maintain a power line across your property. In the case of a conservation easement, this often means splitting off and selling or donating the right to subdivide and develop the property. There are often other restrictions as well, and those are often the subject of negotiation with the organization holding the easement. For an agricultural conservation easement, the landowner still has the ability to farm. What they lose is the ability to carve off a lot and sell it (unless they have excluded a portion of their land from the easement). I'm one of the owners of a jointly owned parcel which has a sustainable forestry easement on it. We can do forest management, but cannot subdivide, build or otherwise develop it.
Here in Vermont, conservation easements on farms are often purchased, providing the farmer funds for improvements, or a way to deal with inheritance issues (for example, give the kid who wants to farm). Up until very recently there was no money behind forestry easements on privately owned land, so they were incidental to the conservation of a farm, or the forest easement was donated by the landowner. That is starting to change, but it's still not a common thing for someone here to be paid for a forestry easement on their land.
In my area, conservation easements do not seem to have a large effect on property taxes. I suspect this is because most conserved Ag or Forest land is already in Vermont's "Current Use" program, which significantly lowers the assessed value of the parcel - probably to well below what the "conserved value" would be. So there is not a lot of incentive for someone to challenge the conserved value of a parcel. I'm told that the owner of a conserved property would have a good argument for reducing their assessment for property tax purposes if they were not in the Current Use program. I've not really searched to see if there is any established case law on this, however.
Those who donate a conservation easement, or sell one at a bargain price do get to deduct the value of that donation from their income for income tax purposes.