Google informs me that it’s Earth Day. Doctor Who is in favour of reusing and recycling, and not just plot ideas.
Aliens have taken advantage of and sometimes exacerbated pollution, global warming, nuclear testing, crude oil treatment, oil drilling, the search for alternative energy sources and volcano-based central heating in Pompeii. The Nestene wants Earth to become an even worse toxic mess to suit its own purposes, the Axons offer new forms of power but want to steal all our energy, and even Davros is happy to take advantage of food shortages to make a quick buck while rebuilding his armies.
I wouldn’t want to get too preachy about environmental issues, but it could add another angle to a Science Gone A Bit Wrong storyline to have protesters outside the gates, offering potential allies to travellers snooping around - or an additional group to spot them and accidentally raise the alarm, or to hit the place themselves and unwittingly release the threat.
Or ripping from the headlines, a blustering tourist business type complaining about wind farms cluttering up the landscape near the resort he’s trying to force through planning permission for. Does he have an agenda beyond wanting an uninterrupted view for his golf course?