1. Introduction

In the previous unit, you read about some of the environmental issues that have arisen from human modification of the atmosphere, biosphere, the hydrosphere and lithosphere. 

A little recap might be in order here. The atmosphere is the air and gases which surround our planet. Humans have changed the composition of this through emitting pollutants including greenhouse gases. The biosphere is the total of all living things which live on the earth. We have changed this by hunting, farming, fishing and logging, amongst other activities. The hydrosphere is all of the water on the planet, including the oceans, but also lakes, rivers, and ice caps at the poles. We have changed this through irrigation, dams, agricultural runoff and through building cities which alter natural water courses. The hydrosphere also includes clouds, fog and precipitation which have been altered through climate change. The lithosphere is the layer of rock of which the planet is composed. We have altered this through mining and through drilling for fossil fuels. 

In this section, we will look at how humans have been responding to these alterations which are having an impact on the health of ecosystems to function. We will also look at how people are responding now and how we should respond in the future to bring about balance so that the planet can function in such a way that all living things can thrive. 

A key term which comes up many times here is the notion of sustainability. You will need to have a good grasp of what this term means and what it means to you. The idea is that we need to live within the means of the planet to provide a healthy habitat to all things and all systems. You will need to come to terms with the fact that there is no agreement yet on what this means. We need to accept, however, that we cannot continue to live the way that we have been without serious consequences for the planet.

Look at the diagram below, which depicts three spheres of sustainability. Do you understand how these concepts all relate? Which terms might you place in the overlapping areas? Are there any terms that you would add?

In this section, you will be asked to consider the ethics of human actions in the past, in the present and to think about how our plans and actions today will affect the future. You will look at the future of cities and will be presented with a few ideas of what we can do to make them sustainable. You will also look at pipelines, which you just read about and will need to decide where you stand on the issue of protesting against pipelines. You will also read about dams and will need to weigh in on whether you consider them to be a net benefit to the world or if some, or all, need to be demolished.