I am a steward of the land that I occupy, or I ought to be. I need to care for the land that is under my control in a long-term sustainable way. I should leave my land more robust, more diverse and more abundant than I found it.
This doesn't mean I have to turn into a technophobe Luddite who eschews (good word, eh?) power tools and backhoes - I love technology and think we should use the best of the tools at our disposal to accomplish our goals. Open Source Ecology is designing and giving away the infrastructure for a do-it-yourself modern, sustainable civilization, and you can build a robot to produce the biofuel for your machines.
Joel Salatin calls himself a grass farmer, but I'll take it one step further and say that we all need to be soil fertility farmers. Think from soil fertility forward to useful yields and I believe that we can't help but take care of the earth.
The other side of the equation - do good and do no harm - also needs some consideration. This is the driver for responsibly handling our waste, and in fact looking to design our systems so that we include the things that call each waste product "food."
This is another one not to take to the extreme - "do no harm" should probably be "do little harm." Doing a little harm, in a way that is sustainable, in a manner that produces a net increase in fertility, diversity and yield has got to be okay. Case in point, raising chickens using paddock-shifting when you don't have enough space to let each paddock regenerate before you need it again. Do you abandon the approach entirely? No, you designate one "sacrifice area" paddock where the chickens eat feed and destroy the vegetation while the other paddocks regenerate. The overall system is healthy and productive.
From the broader perspective, the first ethic is also a call to make big changes. Polly Higgins' work to give the earth itself rights in a court of law is a huge step. For the most part corporations are not actively evil, they are simply motivated by risk (minimize) and profit (maximize), so making Ecocide a crime for which corporate officers can be personally accountable could tip that balance to a much healthier point.
We've only got one planet here that can support our kind of life, and low-impact lift to orbit, much less inter-planetary travel is still the stuff of fiction. The other resources of our solar system are kinda out of reach, so we need to take care of what we have.