The ecological relationship between human society and the planet's environment has become a major preoccupation for thousands of people around the world.
The extent to which we have already changed the world's climate and how much more we will change it is a matter hotly debated by the media and politicians.
Few would deny that humans have an impact on their environment - it is easy to see the connection between a dead fish and a toxic chemical leak into a river.
The more subtle, but nevertheless more dramatic, impact on the whole climate as a result of greenhouse gas emission is the subject of more debate. But few scientists would argue that there isn't a relationship between the gases produced by the burning of fossil fuels since the start of the industrial revolution and the gradual heating of the planet.
Karl Marx and Frederick Engels, when writing about the development of human societies, understood the importance of the relationship between people and the natural environment around them.
Engels noted, when summarising Marx's theory of human history, that "mankind must first of all eat, drink, have shelter and clothing, before it can pursue politics, science, art, religion". This can be applied throughout history, from populations of hunter-gatherers, to the Roman and Greek empires, or feudal lords and their peasants.
This dependence upon nature is crucial to how Marxists understand the further structuring of society. Engels continued his explanation by saying that the "production of the immediate material means, and consequently the degree of economic development attained by a given people or during a given epoch form the foundation upon which the state institutions, the legal conceptions, art, and even the ideas on religion, of the people concerned have been evolved".
For Marxists human society cannot exist without nature. But humans are not simply subservient to nature - since the invention of agriculture farmers have used technology to alter the environment in order to improve the yields of crops that feed, clothe or provide fuel for the rest of society.
Even long before agriculture became a way of producing the majority of society's food, human activity had an impact on the natural world. Possibly the clearest example is deforestation.
The clearing of trees for agriculture by the ancient Greeks led to significant problems with erosion, leading to the silting up of ancient ports and harbours. From the time of the Norman Conquest, Western Europe was significantly deforested as human populations expanded - a process accelerated from the 1500s as the European nations started building huge navies to further their colonial ambitions.
However, prior to the rise of capitalism, such impacts were localised and had a minimal effect on the world's ecological systems. The development of capitalism as the dominant economic system accelerated and intensified the impact of humans on the environment. The economic competition at the heart of capitalism meant that the natural world was viewed very differently.
"For the first time, nature becomes purely an object for humankind, purely a matter of utility; ceases to be recognised as a power for itself; and the theoretical discovery of its autonomous laws merely as a ruse so as to subject it under human needs, whether as an object of consumption or as a means of production," wrote Marx.
Marx understood that capitalism, with its innovative use of technology, its international spread and its thirst to extract the maximum profit from raw materials through the labour of its workers, meant that nature was exploited on a scale as never before.
Ecological insights by Marx and Engels have had to be rescued in recent years by Marxists such as John Bellamy Foster. Traditionally, Marxism has often been accused of being anti-ecological, particularly by those within the green movement.
This has taken two forms. The first is to confuse the appalling environmental record of countries such as the Soviet Union with the actions of a genuine socialist state. The other is to interpret Marxism as being simply about industrial and technological growth, based on human society, with no regard for the planet.
This latter interpretation of Marxism is a crude misreading of the subject.
Both Marx and Engels expressed clear concern for what we would now describe as the environmental consequences of capitalism. In a fascinating description of the consequences of deforestation Engels discussed how, as capitalists are engaged in production for immediate profit, they are only interested in the most immediate results. They are not interested in what happens to the sold commodity, nor are they interested in the natural effects of their activities.
"What cared the Spanish planters in Cuba, who burned down forests on the slopes of the mountains and obtained from the ashes sufficient fertiliser for one generation of very highly profitable coffee trees - what cared they that the heavy tropical rainfall afterwards washed away the unprotected upper stratum of the soil, leaving behind only bare rock!" wrote Engels.
Because Marxism puts the natural world at the heart of its understanding of both capitalist production and human society, it understands how environmental destruction is the logical conclusion of a system built on profit. We see the ecological crisis that we face not as a problem of nature, but as a problem of society. The causes of the problems are social, and their solution thus lies in social transformation.
While in the short term capitalism might be able to deal with particular environmental consequences, it must be replaced by a system that considers the natural world not as a resource to be plundered for short term profit, but as something that needs to be protected and preserved.
Further reading: Ecology against Capitalism and Marx's Ecology, both by John Bellamy Foster. Contact Bookmarks on 020 7637 1848