Hi Peter.

  In addition to State and Federal Governments, there may also be Land Trusts.  I have some property in the mountains, there is a 65 acre conservation easement adjoining on our north side.  That parcel is owned by Nature Conservancy.  They have a very lengthy Deed Restriction that limits/controls any development, access or use to that property.  To our east is another large acreage parcel owned by Naturaland Trust.  Same story, they don't want any development or infrastructure of any kind.

   A different kind of easement is the cross-country powerline about 10 miles to the south.  That goes over people's land; it is owned by Duke Energy in conjunction with the States of South and North Carolina.

  As always, see a real estate attorney before buying, selling, or brokering a property that is affected by an easement.

Most likely they are different in different states and counties.

West VA and VA have different ways of handling conservation easements.

https://www.wvlandtrust.org/protect-your-land/

https://www.loudoun.gov/2816/Conservation-Easements-in-Loudoun-County

They are both state and federal, Peter Mohylsky, Beach Expert 

Be mindful of all the "land grabs" taking place in our country! 

What states today could be stolen tomorrow.

They can be either State or Federal Peter Mohylsky, Beach Expert . My only experience has come from high voltage power lines and Game and Fish easements.

Provisions in AZ Statute for conservation easements

Since only 18% of AZ property is privately owned and we have several large national parks, I believe both state and federal government control various conservation easements in AZ.

State by state rules and Federal can also overlay. West coast we have The Coastal Commission which rules with a whip. You have Florida Oceans and Coastal Counsel. Also strict regulations about water, water runoff, septic, easements for riparian rules and rights. Conservation easements allow past permitted residential use without changes to scenic, wildlife, and open space. They can be between landowner and land trust or person or government or a private company.  Florida has FNIA Florida Natural Areas Inventory which posts a database of 1900 + parcel areas here: https://www.fnai.org/ this does not cover all.  I'm an active member of Pearl River Keepers a non profit working to keep this Mississippi River beautiful and healthy - Florida has MANY organizations like this.  here's a list of some of the 501 c's in Florida that deal with all types of land conservation https://www.causeiq.com/directory/land-conservation-groups-list/florida-state/   

It's not just the Sierra Group that does this there are a thousand entities. 

Yes, they are all different, written to achieve different results.  The one thing they have in common is the objective of limiting landowner rights.

I am not in favor of them, however they are better than outright "Taking" which is what most govt agencies tend to do.

Sorry Peter can not help you.

Oregon is 53% owned by the federal government. We deal with wildlife easements, BLM and national forests. There are some state restrictions as well.

I would say they are different in different states - and even in different municipalities. I've dealt with conservation easements on the lake as well as in-town (a Blue Heron rookery was adjacent to a property that I sold and state guidelines had to be Disclosed).

Looks like you have some great answers here. 

In Massachusetts, the individual communities are allowed to establish stricter environmental bylaws than the State has implemented

Both in my experience and don't think it has changed since I retired. anytime you have a property affected by and easement, consult with an attorney familiar with easement issues. They may contain more than a few surprises.

In Maryland each local County sets parameters for where conservation easements can be placed. There is also a State disclosure addendum to be added if there is one on the property you are selling.

I have no experience with conservation easements. All my business is in urban areas and I have not run into anything other than easements for utilities and such.

US gov owns 47% of all land in the West.

https://www.nytimes.com/2016/01/06/upshot/why-the-government-owns-so-much-land-in-the-west.html