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[passage-header][/passage-header]   When many people think about termites, [1] you think about having to call the exterminator. It's true that termites cause serious structural damage to homes and crops-they cost the United States $2 billion annually in [2] repairs. However, to say that termites are just pests that cause more harm than good would be entirely inaccurate. Out of the three thousand or so species of termites, only a few cause problems for people. The rest are crucial to the health of many ecosystems and are largely responsible for the successful growth of vegetation, upon which all animal life depends. Furthermore, they are capable of astonishing feats of construction and participate in sophisticated social structures.
   [3] From woodlands to a desert to rainforests, termites [4] augment entire ecosystems. As they dig through the dirt, they create holes called macropores, which allow rain to soak deeply into the ground instead of evaporating or running off. The [5] termite's excretions provide the soil with additional structural integrity, helping to prevent erosion. [6] Furthermore as termites dig they mix organic matter like leaves, dead insects, and the remains of other organisms with inorganic clay and sand, helping the soil [7] preserve and retain its nutrients.
   [8](1) Termite mounds can reach up to thirty feet high. (2) To provide some perspective: termites are a quarter of an inch long and build structures that are approximately 1,500 times their heights. (3) The human-scale equivalent would be building a skyscraper over 8,000 feet tall, but the tallest skyscraper in the world is not even 3,000 feet all. (4)The enormous mounds support local ecosystems, allowing water to penetrate deep into the ground and creating moist oases where plants can flourish in arid terrain. (5) Animals also benefit from the presence of the mounds. (6) Many animals, including lizards, aardvarks, and mongooses, burrow into these mounds and use them as homes. 
   [9]Termites were among the first animal species to organize socially, and for the last two hundred million years have developed a sophisticated system of labor distribution. The queen [10] gives birth to nymphs, sometimes 20,000-30,000 per day. After hatching, the nymphs differentiate into classes with distinct tasks. Soldiers protect the mound from ant invasions. Reproductives fly off to form new colonies. Workers build mounds, care for nymphs, and tend fungal gardens that feed the colony. When termites need to evacuate the mound, they do not panic, trample each other, and get stuck in exits as humans often do. [11] Instead, they form orderly lines and wait for it to stand back up and then they all continue on together. Having termites in your house is a problem, but they are remarkable, accomplished creatures that make the world habitable for us all.

[passage-header]Environmentalist Otters[/passage-header]   It has long been known that the sea otters [1] living along the West Coast of North America help keep kelp forests in their habitat healthy and vital. They do this by feeding on sea urchins and other herbivorous invertebrates that graze voraciously on kelp. With sea otters to keep the population of sea urchins in check, kelp forests can flourish. In fact, [2] two years or less of sea otters can completely eliminate sea urchins in a coastal area (see chart).
   Without sea otters present, [3] nevertheless, kelp forests run the danger of becoming barren stretches of coastal wasteland known as urchin barrens.
   What was less well-known, until recently at least, was how this relationship among sea otters, sea urchins, and kelp forests might help fight global warming. The amount of carbon dioxide in the atmosphere has increased 40 percent [4]. A recent study by two professors at the University of California, Santa Cruz, Chris Wilmers and James Estes, [5] suggests, that kelp forests protected by sea otters can absorb as much as twelve times the amount of carbon dioxide from the atmosphere as those where sea urchins are allowed to [6] devour the kelp. Like [7] their terrestrial plant cousins, kelp removes carbon dioxide from the atmosphere, turning it into sugar fuel through photosynthesis, and releases oxygen back into the air. Scientists knew this but did not recognize [8] how large a role they played in helping kelp forests to significantly decrease the amount of carbon dioxide in the atmosphere. Far from making no difference to the ecosystem, the presence of otters was found to increase the carbon storage of kelp forests by 4.4 to 8.7 megatons annually, offsetting the amount of carbon dioxide emitted by three million to six million passenger cars each year. [9]