The phrase "cascading impact" expresses the idea of a result, or series or sequence of results, whose effect gathers intensity as it occurs. It evokes the image of the collective force of water cascading, or falling, from a waterfall being greater than that of water flowing in a river or stream. The phrase, cascading impact, is usually followed by a preposition and an object of the preposition. For example, ... cascading impact over (a period of time), ... cascading impact on (young people's lives), ... cascading impacts of (traffic incidents), ... cascading impact through (all levels of biodiversity). You might rephrase your sentence to say, "overpopulation has had a cascading impact on land resource shortages".

Hi Apple. Think of a cascading waterfall pouring over the edge of a cliff. The kinetic energy increases as the water plummets to earth. You can apply this to the example you provided. Overpopulation increases, or "cascades" over time, creating an effect that gradually (and sometimes not so gradually) becomes worse. Ex: The cascading impacts of poverty after the Civil War crippled the southern, agrarian economy. I hope this clarifies and helps.