Imminent climate change: So what?

By Alan Journet

In previous contributions I have discussed aspects of climate change. In this column I explore six critical consequences.

1. The maximum density of water occurs at about 39 degrees Fahrenheit. Thus, as water cools or warms from this temperature, it expands. Ice floats because it is less dense than water. However, warm water also expands, rises, and "floats." Most importantly, as our oceans warm (as evidence indicates is happening) their volume expands.

Rising ocean level is often naively ascribed solely to melting ice increasing the amount of oceanic water. Melting land-supported ice will elevate sea levels, but since floating ice is already displacing water, when floating ice melts there is no elevation. While ice melt contributes to the problem caused by expanded warming water, predictions vary about the extent of sea level rise.

The 2007 Intergovernmental Panel on Climate Change suggested a 6.5-inch sea level rise during the 20th century, but because it did not include the impact of polar ice melting, estimated at between 18 and 36 inches, the IPCC prediction for this century was among the lowest for the future. However, there is growing evidence that landlocked ice melt (from Antarctic, Greenland and mountain glacier sources) will continue to occur, enhancing the global problem by many yards.

Rising sea levels will undoubtedly not impact Missouri directly, but hundreds of millions of humans across the planet will be flooded out. The refugees will have to relocate somewhere. Additionally, the agricultural production that is permanently lost will need to be replaced. The ultimate cost of rising sea level will be felt worldwide.

2. An argument that some climate change skeptics make is that carbon dioxide is a plant food, so increasing its atmospheric concentration will accelerate plant growth, produce a lusher planet and enhance agricultural production. Biology, however, indicates:

• For most natural systems plant growth is limited by soil nutrients such as phosphorous or nitrogen rather than the carbon-dioxide concentration. For plants limited in this way, no amount of carbon-dioxide enhancement will be beneficial.
• The assumption that all plants are enhanced equally is false. Some plants benefit more than others, while others are unaffected. As a result of this unequal response, the composition of natural plant communities -- including the forest systems from which we gain our timber products -- may be vastly altered.
• Plant species that seem to benefit most from carbon dioxide belong to the category we call weeds -- species that generally grow rapidly in disturbed areas, while among those least affected are crop species. Thus, rather than increasing agricultural productivity, we'll likely see an enhanced need for weed control with an increase in toxic chemicals in the environment.
• The increased temperature that accompanies atmospheric carbon dioxide increase will promote evaporation, drought and probably wildfires. This will benefit neither agriculture nor forestry.

3. Those who travel widely may be aware of geographic patterns in plant communities. Traveling across the United States, for example, we know there are regional zones supporting forests, woodlands, grasslands and deserts. These natural communities determine where our food and fiber production exists. Largely we grow timber in the forests and grow grain in the grasslands.

Potential productivity in these communities is determined by three critical factors: regional temperatures, regional rainfall and regional soil type. While climate change will not affect soil type -- a result of dynamic interactions between plant communities and their substrates -- it will alter temperature and rainfall. Although soils cannot relocate, the optimum climatic conditions for plant species and natural communities will change. Thus, natural communities will suffer negatively while critical agricultural and forestry systems will suffer as optimum climatic locations shift. Indeed, cold hardiness zone maps used by farmers and gardeners already indicate northward climatic shifts.

4. Following the shift of plant communities, many animal species will also shift their distribution ranges. Armadillos and fire ants have already spread north from Mexico, while goldfinches may soon no longer live in Missouri.

5. We should also consider the consequence for temperature dependent species -- such as insects and many other human and agricultural disease organisms and their carriers -- that will exhibit enhanced growth rates and population increases as the climate warms. Disease-carrying insects, for example, are already moving north and to higher elevations, while millions of acres of western pine trees -- probably already stressed by climate change -- have been destroyed by bark beetles. Historically beetles were reduced during cold winters but now survive warmer winters in larger numbers, allowing their rapid decimation of vast areas of pine forest during the growing season.

6. Finally, there is severe weather. Too often, as we witness devastating fires destroying the Southwest and West, we forget that drought increases the debris and dead or stressed trees that fuel fires. Meanwhile, we should recall that warmed oceans foster conditions that induce hurricanes. No longer will we be able to argue that wildfires and hurricanes are acts of God but will have to acknowledge that human activities are -- at least in part -- probably responsible.

We are conducting a huge uncontrolled experiment on the only planet we have. Whether we are conservatives, liberals, progressives, constitutionalists, libertarians or something else, we must acknowledge the potential problem and make individual and collective decisions to respond appropriately. Ignoring the problem will not solve it.

Alan Journet is co-facilitator of the Southeast Missouri Climate Protection Initiative and professor of biology and environmental science at Southeast Missouri State University.