Trees also reduce the greenhouse effect by shading houses and office buildings. This reduces the need for air conditioning by up to 30 percent which in turn reduces the amount of fossil fuels burned to produce electricity. The combination of CO2 removal from the atmosphere, carbon storage in wood and the cooling effect makes trees extremely efficient tools in fighting the greenhouse effect. Planting trees remains one of the most cost-effective means of drawing excess CO2 from the atmosphere. If every American family planted one tree, the amount of CO2 in the atmosphere would be reduced by one billion pounds annually. This equates to almost 5 percent of the amount that human activity pumps into the atmosphere each year.
Some plants and plantlike organisms have developed other pigments to compensate for low light or poor use of light. Cyanobacteria and red algae have phycocyanin and allophycocyanin as accessory pigments to absorbe orange light. They also have a red pigment called phycoerythrin that absorbs green light and extends the range of photosynthesis. The red pigment is found in vegetables. Some red algae are in fact nearly black, so that increases their photosynthetic efficiency. Brown algae have the pigment fucoxanthin in addition to chlorophyll to widen their absorption range. These red and brown algae grow to depths around 270 meters where the light is less than 1% of surface light.
Mr G’s Environmental Systems » 1.1. 3: Energy in Systems