The Problem: high carbon footprint, fossil fuels, high resource demand, light pollution
The Solution: efficiency, good insulation, renewables
Make the switch to LED lightbulbs.
Make any external lighting Dark Sky and Wildlife Friendly- see here for some great tips
Use a blanket and jumpers and turn down the heating a couple of degrees
Invest in good insulation, saving you money in heating bills and the planet
See if you can switch to a renewable electricity supplier. Companies such as Bulb advertise themselves as getting all their electricity from renewable sources. While this may not be entirely true in practice (companies can buy certificates for renewable energy units but get their electricity from the national grid), at least they are making the conscious decision to try and switch.
In the long term, you could look at investing in renewable heating technology, such as solar panels or a ground source heat pump.