下面一段出自2021年高考英语北京卷阅读理解C：

The international scholars’ warning letter doesn’t say exactly what collapse will look like or when it might happen. Collapseology, the study of collapse, is more concerned with identifying trends and with them the dangers of everyday civilization. Among the signatories of the warning was Bob Johnson, the originator of the “ecological footprint” concept, which measures the total amount of environmental input needed to maintain a given lifestyle. With the current footprint of humanity, “it seems that global collapse is certain to happen in some form, possibly within a decade, certainly within this century,” Johnson said in an email.

请问句中的 environmental input 何理解和翻译?