Learn how plants respond to higher atmospheric CO2 concentrations

How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


Global Warming: Can It Be Slowed by Worms?
In an intriguing research paper published in Soil Biology & Biochemistry, Cole et al. (2002) remind us that "it has been predicted that global warming will influence the productivity of ecosystems indirectly by increasing soil biological activity, and hence organic matter decomposition." They also note that "this release of CO2 is expected to be greatest from the organic soils and peatlands of wetland, tundra and boreal zones." Getting even more specific, they report that "in the peatlands of northern England, which are classified as blanket peat, it has been suggested that the potential effects of global warming on carbon and nutrient dynamics will be related to the activities of dominant soil fauna, and especially enchytraeid worms."

In harmony with these ideas, Cole et al. say they "hypothesized" that warming would lead to increased enchytraeid worm activity, which would lead to higher grazing pressure on microbes in the soil; and since enchytraeid grazing has been observed to enhance microbial activity (Cole et al., 2000), they further hypothesized that more carbon (C) would thus be liberated - measured as dissolved organic carbon (DOC) - "supporting the view that global warming will increase C loss from blanket peat ecosystems."

This, indeed, was the established wisdom but a few short years ago: global warming would unleash the great stores of carbon bound in the earth's organic soils and peatlands, leading to a horrendous positive feedback to purported CO2-induced global warming that would fry the planet and bring on every ungodly plague ever to have sprung from the fertile imaginations of the world's climate alarmists. Nature, however, cares little about the machinations of man, marching to the beat of a vastly different drummer, as the study of Cole et al. would soon demonstrate.

To test their hypothesis, the scientists constructed small microcosms from soil and litter they collected near the summit of Great Dun Fell, Cumbria, England. Subsequent to "defaunating" this material by reducing its temperature to -80C for 24 hours, they thawed and inoculated it with native soil microbes, after which half of the microcosms were incubated in the dark at 12C and half at 18C for two weeks, in order to establish near-identical communities of the soils' natural complement of microflora in each microcosm. The former of these temperatures was approximately equal to mean August soil temperature at a depth of 10 cm at the site of soil collection, while the latter was said to be "close to model predictions for soil warming that might result from a doubling of CO2 in blanket peat environments."

Ten seedlings of Festuca ovina L., an indigenous grass of blanket peat, were then transplanted into each of the microcosms, while 100 enchytraeid worms were added to each of half of the mini-ecosystems. These procedures resulted in the creation of four experimental treatments: ambient temperature, ambient temperature + enchytraeid worms, elevated temperature, and elevated temperature + enchytraeid worms.

The 48 microcosms - sufficient to destructively harvest three replicates of each treatment four different times throughout the course of the 64-day experiment - were arranged in a fully randomized design and maintained at either 12 or 18C with alternating 12-hour light and dark periods. In addition, throughout the course of the study, the microcosms were given distilled water every two days to maintain their original weights.

So what did the researchers find? First of all, and contrary to their hypothesis, elevated temperature reduced the ability of the enchytraeid worms to enhance the loss of carbon from the microcosms. At the normal ambient temperature, for example, the presence of the worms enhanced DOC loss by 16%, while at the elevated temperature expected for a doubling of the air's CO2 content they had no effect on DOC. In addition, Cole et al. noted that "warming may cause drying at the soil surface, forcing enchytraeids to burrow to deeper subsurface horizons." Hence, since the worms are known to have little influence on soil carbon dynamics below a depth of 4 cm (Cole et al., 2000), the scientists concluded that this additional consequence of warming would further reduce the ability of enchytraeids to enhance carbon loss from blanket peatlands.

In summing up their findings, Cole et al. say "the soil biotic response to warming in this study was negative." That is, it was of such a nature that it resulted in a reduced loss of carbon to the atmosphere, which would tend to slow the rate of rise of the air's CO2 content, demonstrating once again that nature is well equipped to maintain the mean upper temperature of the planet's surface at a level conducive to the continued existence of life.

Dr. Sherwood B. Idso Dr. Keith E. Idso

References
Cole, L., Bardgett, R.D. and Ineson, P. 2000. Enchytraeid worms (Oligochaeta) enhance mineralization of carbon in organic upland soils. European Journal of Soil Science 51: 185-192.

Cole, L., Bardgett, R.D., Ineson, P. and Hobbs, P.J. 2002. Enchytraeid worm (Oligochaeta) influences on microbial community structure, nutrient dynamics and plant growth in blanket peat subjected to warming. Soil Biology & Biochemistry 34: 83-92.