Human Impact on the Earth's Climate
Human activity in the last 100 years may be leading to remarkably similar environmental conditions as existed at the time of the greatest mass extinction in geologic history: The Permian Extinction (250 million years ago). Since the dawn of the Industrial Revolution, humans have been pumping massive amounts of excess CO2 (carbon dioxide) into the atmosphere. The current level is 380 ppm and rising rapidly every year. At 1000 ppm (the same levels as in the Permian Extinction) the ice caps will have melted entirely, causing ocean temperatures and levels to rise dramatically. The most disturbing part of this scenario is that if all carbon-releasing human activity stopped tomorrow, it would still take another 50 years for the run-away greenhouse effect to begin to reverse itself. Unfortunately, all life on earth is in for an interesting - if not catastrophic - ride for well into this century due to the basic chemistry of the Carbon Cycle that has been well-understood (yet disregarded) for decades.
The extent of our impact on the earth’s environment is nothing short of a devastating yet blind chemistry experiment. Warmer oceans absorb less CO2, which prevents marine algae from performing photosynthesis, thus lowering the levels of oxygen. Without O2 (oxygen), H2S (hydrogen sulfide) metabolizing bacteria thrive (Red Tides) killing off most life, including one of the most important sources of oxygen on the planet: O2 generating algae. When H2S levels rise so high that they come out of solution, this damages the ozone layer, further exacerbating the greenhouse effect. Excess CO2 also causes oceans to become more acidic, stunting coral growth and killing most fragile species. Ocean pH has already risen by .1 pH due to the anthropogenic (human caused) CO2 being absorbed. In addition, the modern era of agriculture has seen an unprecedented and unregulated application of herbicides, pesticides and fertilizers that also contribute in various ways to the chemistry experiment. The use of nitrate fertilizers has stimulated vast phytoplankton blooms in many of our most important fresh water sources. The downstream effect further strips both fresh and salt water of O2, killing marine life and crippling the aquatic web of life that all life depends on. These are just a few of the mechanisms that we know of, that are leading us to climactic calamity. There are surely more that we are not aware of yet, and we are certain to have to allocate precious, scarce resources to solutions as the coming decades unfold.
Without human interference the carbon cycle weaves its way through both living and geologic systems. The connection between the two can seem elegantly simple and fascinating: On land, the carbon cycle starts with plants: Plants take in CO2 during photosynthesis and release O2. Animals eat the plants and release CH4 (methane) in their feces, while taking in O2 and release CO2 during respiration. Certain types of rock, like limestone (which is largely made of the compressed skeletal fragments of marine organisms), release CO2 when exposed to erosion by rain or wind. And herein lies the connection: When the plant dies it is either eaten or decomposed (along with dead animals) releasing CO2 and CH4, or they are compressed into their basic carbon structure and become fossil fuels such as coal, gas, and oil. Without human intervention these fossil fuels are not released into the environment for hundreds of thousands of years (if ever) and even when they do escape into the environment, it is only by tiny increments. In marine environments, algae perform similar functions as plants on land. Through photosynthesis the algae extract CO2 while releasing O2. Fish take in O2 from the water and release CO2. They also release NO3 and PO4 in their feces. When algae or fish die, they sink to the bottom and release C6H12O6, or are eaten by other animals, or are compressed into fossil reservoirs of oil, gas or coal. When small marine creatures with shells die, they fall to the bottom and become the important layers of sediment that scientists study to learn about earth’s history. Some of the CO2 in the oceans escapes, making it available for plants and starting the cycle all over again. For hundreds of thousands of years, these geologic and living systems have stayed in near perfect balance, and now we will have to manage the consequences of our intervention.
In discussions about climate change, the subject of burning fossil fuels usually gets most of the commentary, but one of the keys to understanding the importance of the earth’s CO2 balance, is appreciating the far-reaching consequences of the agrichemicals: also an invention of the last 100 years. The delicate balance between Aerobic Water (oxygenated) and Anaerobic Water (low to no oxygen) is heavily affected by human's use of nitrate fertilizers. Runoff from agricultural fertilizers deposits excess PO4 (phosphates) and NO3 (nitrates) into bodies of water. Nitrates and phosphates stimulate surplus plant growth, which blocks sunlight to the lower levels of the water column. Less light decreases photosynthesis. Plants (that produce oxygen) die off. This triggers a rise in bacteria involved in decomposition, which releases more nitrates and phosphates, further aggravating the problem. The aerobic bacteria trying to decompose all the plant waste use all of the oxygen up. Different bacteria, that are anaerobic, continue to carry on decomposition reactions with drastically different products. CO2 is converted to CH4 (methane) and S (sulfer) to H2S (hydrogen sulfide) during decomposition in low oxygen conditions. H2S metabolizing bacteria bloom in this toxic soup, creating more H2S and CH4. The extremely acidic water kills all remaining life, which in turn affects the broader life systems that once depended on that water source.
In short, when humans introduce Excess CO2, PO4, NO3, CH4, S, and SO2, the cycle’s checks and balances are altered, if not destroyed:
· Humans burn fossil fuels pumping massive amounts of CO2, CH4, and SO2 into the atmosphere.
· Human’s knack for slashing forests reduces the amount of large plants that would otherwise sequester (capture and hold on to) vast amounts of the excess amounts of CO2 and release Oxygen.
· Human’s mismanagement of grasslands is causing rapidly advancing desertification all over the globe, which also reduces the amount of plant life available to absorb the excess CO2 and release Oxygen.
· Reduced plant life leads to excess CO2, increasing the greenhouse effect causing rising global temperatures.
· Human agricultural practices strip both fresh and salt water of O2, killing life and crippling the aquatic web of life.
· SO2 (sulfur dioxide) condenses into acid rain, which kills plant life, and poisons water when it falls back to earth.
Just as humans have the power to cause the previously detailed problems, they have the ability to restore balance. It will take all the will, compromise and creativity that my generation can muster. There will be those that participate by adapting their daily choices and activities to suit the new reality we face, and there will be the scientific warriors and creators that help the planet fashion a new way of living that is sustainable at every level. As for solutions or remedies to the problems we cannot escape at this point, I am constantly contemplating various combinations of new approaches and I hope there are many more young scientists doing the same. My ideas are still in the formative stages, but here is one seed of an idea: I can imagine a device or simple addition to all unused horizontal surfaces on buildings and city rooftops, that I like to call “plant pod”. It is essentially a green house, large or small, that makes use of the wasted horizontal and vertical surface square footage in cities. The plants inside take in the CO2 from the surrounding air and expel oxygen through photosynthesis. These plants can eventually be included in the food source cycle for the inhabitants of the city.
Civilization will need solutions that retro-fit our current environment - like my own small idea - but mainly it will need mounting responses from regular citizens that may run completely counter to many of our most preciously held expectations. We will have to come to grips with such delicate subjects as population control. We will have to redefine the things we aspire to as quality of life matters like unlimited fresh water, luxury consumerism, and limitless food choices. One thing for certain is that the developing world cannot aspire to live like Americans and the rest of the consumption-oriented societies. By now, almost everyone has heard the calculation that goes something like: If everyone on the planet lived as largely as an American, we would need 2 ½ earths to sustain that level of consumption of resources. That may have to be our guiding principle as we who have much, are forced to conserve, and those who have little aspire to a more comfortable life. For the next 50 years, at least, we can hope for the best and prepare for the worst. Perhaps by simply creating a global understanding of the grand chemistry experiment that we are engaged in, we will take the first step in re-balancing the Carbon Cycle and restoring the future of life on our planet.