Well, unless he plans to lay waste to what has already been built, I feel like we're heading into a long history of undo/redo by new presidents when the party switches.
My only possible comfort is that Trumpism may split the Republican party to the point that they are no longer viable in a national election.
Well taking those in reverse order.. first of all yeah I hope he does split the party... but I read today that McCarthy is meeting with Trump in Florida soon and I would expect will be trying to find a way to keep the hassle with Liz Cheney and similar minded Republicans in the House smoothed over and not hostile to Trump at least in the short term.
As for the raft of EOs Trump signed and now Biden signs to reverse, it may not be such a precedent setting thing for our future. It may look that way now, but primarily because Trump was about cosmetics and wrote up more EOs with fewer legislative backups than are usual.
Congress declined to back up many of the EOs Trump signed that did require further underwriting by that branch of government. As a result, Biden has far less trouble reversing by EO what Trump did not manage to convert into lasting policy changes. Even one of his own former advisor had joked that everything except the judicial picks would be gone by sunrise this past Monday. Not quite true, but that pile of EOs Biden is tackling is quite a stack. Some will end up in court. A lot of Trump's did as well.
On the matter of the pipeline halt: oil sands extraction in Canada is a fairly dirty process involving strip mining, heavy reliance on fresh water supplies while producing both toxic emissions, toxic tailings and waste ponds that threaten migrating birds. It's also a fairly expensive process for those very reasons (or to mitigate them), at least compared to the less well tested but far less disruptive and less toxic extraction process that has been tried in Utah, involving recyclable solvents in a closed system. But it has remained to be seen whether the latter process could profitably be scaled up. Last time I looked into it, only thing I noticed was the company that was trying that out had changed its name from one alphabuzz combo to another...
Process aside, the product that would be shipped via the planned pipeline to the US Gulf of Mexico is diluted bitumen, a problematic fluid in that health risks due to ruptures and emissions at pumping stations are not fully understood.
So when speaking of "laying waste" to what has already been built, it's important to take into consideration what could be laid to waste if the pipeline were to be completed and put into operation.
As for the loss incurred due to project halt: most work on the pipeline extension had already been stopped prior to launch of the Biden administration due to anticipation that the permit would be rolled back. It's true that around 150km of line had already been constructed in Alberta, so yes, TC Energy has now encountered a material downside it had warned could be incurred, and it has said it will not now proceed to lay line in Saskatchewan. Only about 2km of line was laid across the US border as a symbolic move after the Trump administration had withdrawn regulatory resistance.
If we want to get real about climate change mitigation, it's important to leave as much fossil fuel in the ground as possible, and focus on renewables for energy production. To meet demand for plastics, we should already be reserving petroleum-based formulations for critical supplies like IV tubing snd not be using it needlessly for making toys, or even in consumer products packaging in most instances.