What is a sustainable practice?
A practice where the use of a resource is balanced by the renewal of that resource.
If the use of the resource exceeds the renewal of that the resource the resource will be depleted. If the use of the resource greatly exceeds the renewal capabilities of the resource the resource may cease to exist.
The well managed use of forest is an example of a sustainable practice. The rate at which trees are cut down is regulated to equal the rate at which trees can be replanted and grown.
The fishing of salmon is another sustainable practice. The number of fish allowed to be harvested is regulated to allow enough Salmon to make up it upstream to regenerate the population of salmon.
The fishing of anchovies off the coast of Monterey in California is an example of a non sustainable practice. So many anchovies were caught that the breeding population dropped to near zero. Presently there are no anchovies to fish off the coast of Monterey.
The harvest of Otter skins is another example of a non sustainable practice. The otters were hunted to near extinction. Today the otter is still a protected species and no hunting of these scares animals is allowed.
Resources have to be carefully managed so that sustainable practices ensure that the use of the resource does not exceed the ability of the resource to be regenerated.