The Cold War was characterised by significant distrust, suspicion and ignorance (promulgated in propaganda such as the triffid-like poster pictured). It was designated a cold war because the primary enemies never fought each other directly, although proxy conflicts arose in satellite states such as Korea and Vietnam.
Though the concept of 'the population explosion' was not in vogue when this novel was written (Paul Ehrlich's The Population Bomb was not published until 1968), Wyndham makes it clear that the consequences of rapidly increasing human numbers were starting to worry people.
The 1950s was the decade in which the human population began rapidly to escalate: at the beginning of the decade the world's population was about 2.3 billion; it increased to nearly 3 billion by 1960. Wyndham's 25 million extra mouths per year was correct in 1951, but the rate of increase jumped to nearly 50 million more each year during that decade.
Trofim Lysenko was in charge of the Soviet Union's biology program under Stalin.
Lysenko was an agronomist who favoured Mendelian genetic manipulation. Soviet biologists were particularly interested in plant hybridisation.
Because of its abundant wildlife, varied climate and winter activities, it is becoming popular with tourists.
This is in opposition to a biological observation known as Bergmann's Rule, which states that within a widely distributed genus, species in colder regions tend to be larger than those in warmer regions. However Bergmann's Rule is mainly applied to birds and mammals (such as humans).