Surely Earth is too big for humans to impact it too much...
Many people think that Earth is so large that human activities couldn't possibly be making much of an impact on the planet. But human populations have expanded at a more than exponential rate and it is human ingenuity from advances in farming that has kept so many people alive. The map above depicts a quantitative analysis of human influence around the world. Low scores are the least human influence; higher scores are greater impact. Taken into account were population density, land transformation, human access, and power infrastructure. Human access and land transformation alter ecosystems and bring in pollution and invasive species, which decrease biodiversity. This chapter explores some of the impacts that humans have had on Earth's systems.
Human population grew by 1 billion in the past 12 years to reach 7 billion. In 1960, the human population was only 3 billion. The population growth of every species on Earth is limited by some limiting factor so that within each ecosystem the carrying capacity for each species is set. Human ingenuity due to our brains and our hands, has allowed us to blow past any previously held idea of what Earth's carrying capacity for humans is. The development of and advances in agriculture over for the past 10,000 years have been the largest factors. How long can human population continue to grow? No one knows, and no one knows what the planet's ultimate carrying capacity for humans will be. The enormous number of people, and the tremendous consumption of the percentage of the world's population that does more than just meet its basic needs, has put a strain on Earth's resources and generated a tremendous amount of waste. Land is used for farming and other activities and also for the disposal of hazardous wastes. Water is used for drinking, bathing, agricultural and industrial uses, which may deplete supplies and pollute water sources. Much of what has fueled development in agriculture and industry has been the availability of cheap fossil fuels, which pollute the air and emit carbon dioxide into the atmosphere. Carbon dioxide is one of the greenhouse gases that trap heat and moderate Earth's temperature. As the levels of carbon dioxide and other greenhouse gases in the atmosphere rise, they can trap more heat, which causes global temperatures to warm. The effects of global warming are already being seen as ice melts and sea level rises, species are forced to move uphill or higher in latitude seeking a suitable habitat, the oceans become ore acidic, and many other consequences.