Regarding the preservation/taxation discussion:
I grew up in the next town over from Westport (Dartmouth) - parents still live there. Both towns are in the middle of a conversion from town/center - rural area to suburbia. Dartmouth has had a mall and associated retail for years, but also many, many acres of farms (It is one of the largest towns landwise in MA). The conversion used to be gradual, but has accelerated significantly.
The area is approx 1 hour south of Boston, 40 minutes east of Providence, RI. The local cities - Fall River & New Bedford (former textile & whaling giants) are both in economic distress. It is only in the last 10 years that Westport & Dartmouth have been considered "bedroom communities" for Boston & Providence metro areas. As such the rate of development today is overwhelming.
The goal of preserving land (whether it be land trust, as in this case, or the town itself buying it) is a - to preserve it (duh), and b - to slow the rate of growth in town. Some towns limit the number of building permits each year, others (especially cape cod) create special restricitons that most of the new building is not for year round use - ie you get to pay taxes, but don't have a valid residency to put your kids into the school system.
Town govt. in many areas is going bankrupt because they can't keep up with the pace. Maintaining the level of service (primarily schools, but also public safety etc.) that attracted the new residents is very expensive. New schools cost lots of money significantly adding to the "overhead". For example - consider the school that was built 20-50 years ago - it's debt (bonds) has long been retired. Never mind that it cost a fraction of what a new building costs today. If adding 10% to the school system requires a new building, it could well double the cost of education in town (depending on how many buildings the school system already had). It's the interplay of the fixed (buildings) & variable (# teachers) costs that come into account.
Limiting developable land has unitended consequences though. It artifically raises property values. You won't see many current town residents complaining, but it makes it more expensive for new residents to move in.
I don't think anyone can stop suburban sprawl unless you tore up all the interstate highways that enable "reasonable" commute times to the cities/metro areas for employment. I wonder if Eisenhower intended to create suburban american when he created the interstate system???