Another way to look at whether an activity is sustainable or not is through the simple lens of regenerative versus degenerative.
These terms are frequently used in permaculture, a discipline that asks how we–as humans–can sustain ourselves and provide for our needs and the needs of the living world for an indefinite period of time.
To regenerate, biologically speaking, is to grow again after being lost, damaged, or destroyed. It is to give new life to a community of beings that has been weakened or dangerously disturbed.
To degenerate is to change to a worse state or condition: to become worse, weaker, less useful, etc.
An activity that builds soil, improves the local water cycle, and enhances native biodiversity and biological integrity at no expense to another locale is regenerative. Any activity that fails to do these things is most likely degenerative. For example, building small check dams in drainages with locally-found rocks is regenerative because the dams slow, spread and sink rainwater into the ground instead of letting it run off into a creek or river. This improves the local water cycle and increases habitat for plants, insects and microbial life with no ill-effects on any other lands. On the other hand, building similar check dams with newly poured cement, while offering the same local benefits, results in damage being done elsewhere by supporting the industrial mining, manufacturing and shipping of portland cement. Likewise, irrigating a small garden with rainwater you have captured, stored and transported to your garden via salvaged pipe or non-eroding earthworks is regenerative, while doing the same thing but depending on the regular purchase of plastic tubing to distribute the water has a net degenerative effect, as the embodied energy and toxins of plastic and its centuries-long damage to life as it breaks down far outweigh the regenerative effects in your garden. Of course if you pump water from a well or a creek, your degenerative effect is increased, as the use of fossil fuels or electricity cause even more damage–sacrifice zones–to lands and life both near and far.
We encourage the use of this simple framing as you approach your daily activities, especially your land management practices. Of course, a transition to a truly regenerative life can’t be had overnight, but the more you think about this and strive to achieve it, the healthier the land will become.