[Below is a re-working of a section from a paper Speculative capital and the ecosystem of globalization. I've been thinking that forms of capital are key to understanding changes in the human-nature relationship in the capitalist era.]
Forms of capital and the human-nature relationship
Marx explained that Capital is not just forms that wealth takes, but that ultimately it is a social relationship. Money, or wealth, becomes capital when it is applied to its own self-expansion -- money used to make more money if you will. But in that process of self-expansion, capital describes a way that people are organized in the process of production. The social means of production are owned privately, through control of the production process one class accumulates the surplus labor of another class, this accumulated "dead labor" in turn is invested in expanded circuits of production. In the process, capital expands and the power and wealth of the owning class grows along with it, allowing capital, or the class that expresses it, to exert even more control over the production process, and to appropriate more surplus labor.
While capital is ultimately a social relationship, this relationship is expressed in the forms the dead labor takes: money capital, productive capital, industrial capital, merchant capital, and so on, depending on the role that it plays at different moments or stations of the circuit of capital. Likewise, capital takes different and new forms over time, as the means of production develop, the circuits of capital expand, the capitalist system matures, as the credit system deepens and becomes more complex, etc. For example, the forms that capital could take in the early days of mercantilism or agricultural capitalism are different than the forms that capital can take in the age of steam power or in the age of electronics.
The economy describes the overall interaction of humans and the environment in production and reproduction processes. The environment is the beginning-and-end of production, the original source of material and wealth, the economy is just a process of rearranging the environment. [One could cite Marx here I think, but is it necessary?] If we think of forms of capital as structures through which economic activity takes place, it follows that they are the means through which we interact with the environment -- the forms of capital also signify aspects of the human-nature relationship. Capital structures imply a particular relationship to the world.
Forms of capital -- as structures through which people interact with the environment -- I suppose these are really a subset of forms of property. Property relations also describe a particular relationship to the world. Once things become titled (in the legal sense, or deeded), i.e. owned, they also become "things", so to does the world, the environment. [Here Marx's lead-in to the discussion of the fetishization of commodities in Capital Vol I, Chapter I is relevant.] I think there are a number of writings that celebrate e.g. native American relationships and other original communist forms of social organization and (non)property to the environment.
Whether these things are held in common, shared, or bought and sold, or bought and sold on credit, or bought and sold -- not the things themselves, but as abstract pieces or shares, or not the shares, but the movement in price of the shares, and so on -- these qualities or degrees of relationship are mediated by social relations, and in the case of private ownership, at least in the "modern era", say from 1750 or so on, by capital structures. A worker, a family, even an enterprise interacts with and is integrated into the economy through capital forms which in turn will affect production or laboring, and through that the environment. Alienation to the economy (and the environment) is shaped by these capital forms.
For example, to take a current example with the so-called "housing bubble", a mortgage, which presumes a relatively developed financial system, allows a worker to acquire a home with "just" the down payment, but also requires the ongoing acquisition of cash to pay principle and interest; binding the worker into cash economy, i.e. commodity exchange. That mortgage can then be pooled with mortgages of other homeowner, and sold in the financial markets, attracting more capital for lending, reducing the cost of money (interest). This securitization allows mortgages to be extended to more borrowers, which feeds a housing boom (and allows more risk in economy). The expanded credit expands the market for new home construction, leading to urban sprawl, and with limited or non-existent mass transit, to the need for more cars and highways and fossil fuel consumption, greenhouse gases; also habitat loss, which contributes to species loss; also consumption of forest products and minerals; and so on. There is no getting away from the environment.
Grain futures provide another example. They function in a similar way to credit, allowing an expansion of economy. But as Cronon (1991) points out, the grain futures requires at the same time an anonymization of nature, where the individual wheat plant tended by the individual farmer disappears as individual and is merged with the grain from other farms into carloads of a class of wheat. The capital structures facilitate a different degree of alienation from agriculture and nature. Cronon's analysis shows how this change is reflection of necessary changes in the production/transportation process if the economy is to take advantage of what rail technology makes possible.
So capital structures can be an entry point for understanding the changing relationship to the environment. And inasmuch as the development of capital structures moves in a stage-wise fashion, in dialectical tandem with the development of the means of production and especially the means of communication and finance, they become another entry point for understanding how particular environmental forms or structures or relationships emerge at different stages of capitalism.
Next: speculative capital and the ecosystem of globalization