The original Earth Day on April 22, 1970, billed as “The First National Environmental Teach-In,” came about with the mounting concern that the global environment was slowly being disassembled. Humans were consuming natural resources faster than the planet could renew them and future sustainability of life on the planet, as it was then known, was questionable.
Rapid population growth, disappearance of plant and animal species, and air and water pollution were combining to bring mounting pressure on the environment.
Human population in 1970 was 3.5 billion. The “Zero Population Growth” movement was expected to slow down growth. It didn’t work. Now, on the 43rd Earth Day, world population is 7 billion and growing by 80 million a year, the equivalent of twice the population of California.
Then as now, species extinction and loss of biodiversity were caused largely by loss of habitat, a result of human encroachment on open space by urbanization and expanding agriculture necessary to feed the growing population. Loss of species was addressed in 1987 when the California Department of Fish and Game released a report on native species listed as threatened or endangered and those likely to meet listing criteria. The result: mammals, 33 percent; birds, 23 percent; reptiles, 31 percent; amphibians, 40 percent; and fish, 41 percent.
Air pollution in 1970 was mostly about smog over large cities. However, some atmospheric scientists were beginning to be aware of human-generated CO2 and other gases in the atmosphere as possibly having an effect on the planet’s climate. Forty years later, we realize that climate change is the single most threatening environmental problem facing all humans.
One scientist who was aware early on is James Hansen, the director of NASA’s Goddard Institute for Space Studies. Hansen created the world’s first climate models more than 30 years ago and he has used them to predict most of what has happened to the climate since then. In 1981 he published a paper in Science Magazine that predicted correctly that the 1980s would be unusually warm and that the 1990s would be even warmer.
In a December 2008 letter to Barack and Michelle Obama, Hansen said, “A stark scientific conclusion, that we must reduce greenhouses below present amounts to preserve nature and humanity, has become clear. It is still feasible to avert climate disasters, but only if policies are consistent with what science indicates to be required.”
Atmospheric scientists use the acronym DAI, meaning dangerous anthropogenic interference,to represent the amountof CO2 in the atmosphere, expressed as ppm (parts per million)to indicate the threshold beyond which climate change will be largely irreversible. Many in the scientific community believe that DAI is around 450 ppm of CO2. Hansen believes that 350 ppm is dangerous. The most recent measurement is 385 ppm.
Since 2000, with a few exceptions, each year has been warmer than the preceding one. Last year the U.S. was the hottest it has ever been in the 118 years that records have been kept. The recent intense storms in the northeast U.S. and in other parts of the world are believed to have been influenced by climate change.
Polar sea ice, as well as ice sheets in Greenland and Antarctica, are rapidly melting. According to an April 2010 article in National Geographic, glacial ice on the Tibetan Plateau and adjacent Himalaya mountains is also melting rapidly. This ice is the source of Asia’s largest rivers, the Yangtze, the Yellow, the Mekong and the Ganges, which together supply fresh water to 2 billion people, one-third of the world’s population.
Closer to home, in 2003, major infestations of the pine engraver bark beetle have killed millions of pinyon pine trees in the American southwest. In recent decades similar outbreaks of the spruce bark beetle have decimated 4 million acres of Alaskan boreal forest. And the mountain pine beetle has been attacking lodgepole pine in Montana, Colorado, Wyoming and British Columbia.
Bark beetle outbreaks are not new in western conifer forests, but the severity of these outbreaks is alarming and believed to be caused at least in part by drought-stressed trees and warmer, longer summers advantageous to the beetles.
Trees killed by bark beetles slowly release CO2 as they decay. When burned, they release CO2 much faster, adding to greenhouse gas concentrations, which cause warmer summers and drought conditions, which in turn encourage beetles, etc. This is an example of what ecologists call a “positive feedback loop.”
Even closer to home, conifer forests in the Sierra, already unnaturally dense resulting from past management practices and 100 years of fire exclusion, are becoming more vulnerable to warmer weather and drought conditions resulting in the potential for more intense forest fires. Local problems can be addressed locally. Forests can be thinned to reduce vulnerability to fire and insects.
However, worldwide climate problems will require worldwide solutions involving all nations on the planet. The international cooperation necessary to halt climate change may be mankind’s greatest challenge.