Lan Wright, The Last Hope of Earth (1965).
The year is 1985 and the Earth is in pretty bad shape. A strange aquatic weed has proliferated madly, choking all the world’s waterways, making sea travel impossible, and killing off marine life. If that wasn’t bad enough, the omnipresent weed’s waste products create a greenhouse effect that rapidly melts the polar ice and floods the world’s coastal cities.
Economic collapse, political upheaval, refugees, war, crime, famine, and disease follow in the wake of the unfolding chaos.
In the short time man has before the complete collapse of civilization, our hero must establish a human colony on Mars.
But there are some secrets about Earth and Mars and Mars’ moons that nobody’s told him…