Final answer:
The key ecological resource for protecting the Pine Barrens in the 1960s is not specifically mentioned, but likely involved principles from the Multiple Use Sustained Yield Act of 1960.
Step-by-step explanation:
The ecological resource key to protecting the Pine Barrens when it was threatened by development in the 1960s wasn't specifically named in the provided resources. However, it's possible that the resource was related to the overarching conservation principles of the time, such as the Multiple Use Sustained Yield Act of 1960, which aimed to balance environmental and human needs by promoting outdoor recreation, timber, watershed, and other uses in a sustainable manner.
As for the efforts to protect a species creating tensions between environmentalists and workers in the Pacific Northwest in the 1980s and 1990s, it was likely the northern spotted owl, a case famously associated with clashes over conservation and logging jobs.