Trevor,
It is good to see you reading some Heidegger. Most read him in terms of the German philosophical tradition or existentialism.

I read him in terms of the Australian environmental philosophical movement that was inaugrated by the Routley's transgressive Fight for the Forests book of the early 1970s.

Why so? If you read this brief overview you will see that they contested the economic arguments of the utilitarian state forestry industry and they defined the conflict as one of values. There was nothing about metaphysics or ontology, despite the human-centredness and subjectivism of utilitarianism.

What we got was an account of the problems given in terms of the state forestry industry and profession and their ideology of maximising wood production. What was missed was the philosophical framework that the deology was a part of. What we got was the politics about foresty as a captured bureaucracy--but not the ontology of utilitarianism.

With Heidegger you re-read the text with an eye to the ontology. That is an important step in the context of this kind of Australian environmental philosophy that would have instinctively rejected Heidegger.