Fossil Food
We're used to the idea of using fossil fuel, indeed we depend upon it heavily. But consider how one's future might look if it was necessary to eat fossil food in order to exist.
That is just the situation faced by certain aquatic larvae and shrimp- like crustaceans living on Alaska's North Slope. Their cousins living in warmer climes subsist year-round by eating microscopic photosynthetic plants that grow in the water or on rocks and mud at the bottoms of ponds. However, on the North Slope, the growing season is too short to grow enough food for the little critters to eat all winter. They make up the deficit by eating peat, in a secondhand sort of way.
Peat has been accumulating on the tundra since vegetation was reestablished on the North Slope about 12,000 years ago, when ice age glaciers receded. Today, the vegetative residue of 12,000 years is present as a layer of peat 1-2 m (3-6 feet) thick overlying the tundra and topped by the living plants of today. Only the top foot or two thaws each summer; the rest is solidly frozen as part of the permafrost layer. However, at lake shores, riverbanks or at the coastline, the permafrost is exposed to summer warming, then blocks of peat and soil topple into the water to be thawed and dispersed by currents or waves.
Bacterial populations grow on this organic matter and other microscopic animals feed upon them. Insect larvae and the crustacea then feed upon these organisms, and thus the peat carbon, is passed up the food chain as a constituent of each link. The food chains are very similar to those utilizing aquatic plants or tundra vegetation growing today, but a delay of several thousand years has occurred between the plant growth and consumption of the vegetation.
It is possible to determine the extent to which any species of fish, bird or invertebrate depends upon the "peat subsidy" by analyzing the radiocarbon content of its tissues using standard radiocarbon dating techniques. Since peat is several thousand years old, any organism feeding upon it acquires an apparent radiocarbon age proportional to its dependency on peat in its food chain.
As might be expected, pronounced seasonal shifts occur as aquatic plants become available in summer. Grayling in the Colville River depend almost entirely on the seasonal plant growth (via flying insects) during summer, but, as winter forces shifts in feeding habits, they acquire about 33 percent of their food energy from peat.
With other species the peat subsidy is even more pronounced. The least cisco (a species of whitefish) feeds in the nearshore marine environment during summer but then shifts to peat-based food chains for almost 40 percent of its energy requirements during winter. An old squaw duck reared in tundra ponds contained an astonishing 64 percent peat in its makeup.
The fish, ducks and other birds surely don't think about it, but unless their intake of fossil food is slower than the rate of peat growth, someday they will have to change their winter eating habits. Of course, the long delay between the formation of the peat and the time it is eaten means that any changes that do take place will occur very slowly.
