The Nitrogen Fix

I believe this book was published in 1980 but the title and picture cover harks back to earlier days of science-fiction. Hal Clement's planetary vision (in this case, Earth) is every bit as realised as his other planetary creations. In this case, Clement uses his science-teacher background to present an Earth of the far future that has lost most of its oxygen, forcing humans to live a nomadic existence that is harsh and short-lived. The lack of oxygen of course has reduced the human population drastically - it is only a matter of time until the human race ceases to be. Clement's portrait of a world whose atmosphere has changed seems very plausible (no nukes, no wars, no asteroids - just natural and man-made changes to the atmosphere). Clement's argument is that all planets that have an O2 rich atmosphere eventually lose it (this is explained in greater detail in the book). The alien lifeforms are well described, but (as you can see on the cover) their appendages would not make them very good at building high-tech gadgetry, though somehow they manage to get from the comet they were on to the Earth's surface. Still, Clement gives the aliens a pretty credible biology. There is a reasonable level of suspense (Clement is not really known for his suspense, e.g. Noise, Half-Life), based around the conflict between the 'city' dwellers and the outcast nomad family, as well as the usual xenophobia towards the alien creatures, which causes some anxious moments. I won't give away much more, but for those who are familiar with Clement and are not put off by a bit of hard science (in this case, chemistry) then I thoroughly recommend this book, which for me was a hidden gem of science-fiction. Another interesting aspect (later repeated in the 'finger language' of his novel, Noise) is Clement's description of a sign language that has naturally evolved among the nomads (who live almost exclusively outside in the harsh Nitrogen atmosphere) as a consequence of having to wear oxygen masks all the time. It is this sign language that also enables the nomads to communicate and eventually bond with the aliens.