TO SAY THAT ''human activities now match or even surpass nature as an agent of change'' is an environmental cliche. So too is the statement that ''although the full long-term implications of these [human-made] changes are as yet unclear, there is a growing perception that the future welfare of human society is to an unknown degree at risk.''
Yet such statements are true. As a trenchant new analysis of that challenge published Monday by the United States National Academy of Sciences notes, ''our current scientific understanding amply justifies these concerns,'' substantial uncertainties notwithstanding.
This is not environmentalist propaganda, of which we have a surfeit. There's no hand-wringing claim that the sky is falling. But the analysis from which the above cliches are quoted clearly shows that there is indeed a cloud of concern much bigger than a man's hand now looming above our horizon. It correctly concludes that ''global environmental change may well be the most pressing international issue of the coming century.''
If you are interested in the dimensions of environmental changes that will touch everyone on Earth but distrust environmental hype, this is the one book to get. Entitled ''One Earth, One Future: Our Changing Global Environment,'' it emerged from a forum held in May 1989 at the academy.
One ''critical fact'' sets the discussion's perspective. Citing the unexpected appearance of the Antarctic ozone hole, the report notes: ''The discovery brought home a critical fact about our planet. No matter how much we learn about the workings of the earth system, the unexpected always occurs.''
This does not mean that human depredation may unexpectedly destroy the planet as an abode for life. The academy analysis has little use for the naive fear that Earth is a ''fragile and endangered planet.'' It says ''this phrase almost certainly exaggerates the case.''
Noting that Earth has endured eons of massive geological change and that organic life generally has proved resilient, it observes that ''no matter what we humans do, it is unlikely that we could suppress the powerful physical and chemical forces that drive earth systems.''
The danger lies in the clear possibility that we may make the planet unpleasant for ourselves even though organic life in other forms may thrive. Humankind could, by its own actions, become irrelevant to the planet's future.
The analysis cites pollution-driven changes in atmosphere composition and chemistry, deforestation and the like as the major factors of concern. These combine to drive environmental changes -- especially climatic change -- at a pace far faster than natural systems can adapt.
Such rapid change ''could cause regional food shortages, create waves of environmental refugees, and threaten security of other countries as the effects of turmoil ripple through the world
We are already committed to some of these changes. But their pace can be slowed and their effects ameliorated. Recommended actions include energy conservation and other measures to cut pollution, forest preservation and restoration, recycling and wiser use of materials. It's a familiar list.
The goal, the study notes, should be to build resilience and adaptability into the world economic system. This can only be done if rich developed nations, acting from enlightened self-interest, help poorer third world countries take the costly necessary economic measures.
The message is clear. The need is not for humanity to learn to manage the planet, which can manage quite well without us. The need is for humanity to learn to manage itself.