The answer to this question recognizes two major points. The first is that the human impacts on the environment are manifested in several issues, many driven by common factors associated with the meeting of human needs. The second is that many of these issues -- their causes and impacts -- are biogeophysically and socio-economically interrelated. With a central emphasis on climate change, this answer assesses the current understanding of the interrelations between the causes and impacts of the key environmental issues of today. To that is added a summary of the now largely separate policy approaches to these issues. In so doing, this answer frames how choices associated with one issue may positively or negatively influence another. With such knowledge, there is the prospect of efficient integrated approaches.

Meeting human needs is degrading the environment in many instances, and environmental degradation is hampering the meeting of human needs. Society has a range of socio-economic paths to development; however, these will only be sustainable if due consideration is given to the environment. Environmental degradation is already evident at the local, regional, and global scale, such as air pollution, scarcity of freshwater, deforestation, desertification, acid deposition, loss of biological diversity and changes at the genetic and species level, land degradation, stratospheric ozone depletion, and climate change. Very frequently, addressing human needs causes or exacerbates several environmental problems, which may increase the vulnerability to climatic changes. For example, with the aim of higher agricultural production, there is increased use of nitrogeneous fertilizers, irrigation, and conversion of forested areas to croplands. These agricultural activities can affect the Earth's climate through release of greenhouse gases, degrade land by erosion and salinization, and reduce biodiversity. In turn, an environmental change can impact meeting human needs. For example, agricultural productivity can be adversely affected by changes in the magnitude and pattern of rainfall, and human health in an urban environment can be impacted by heat waves.

Just as different environmental problems are often caused by the same underlying driving forces (economic growth, broad technological changes, life-style patterns, demographic shifts (population size, age structure, and migration), and governance structures), common barriers inhibit solutions to a variety of environmental and socio-economic issues. Approaches to the amelioration of environmental issues can be hampered by many of the same barriers, for example:

• Increased demand for natural resources and energy
• Market imperfections, including subsidies that lead to the inefficient use of resources and act as a barrier to the market penetration of environmentally sound technologies; the lack of recognition of the true value of natural resources; failure to appropriate for the global values of natural resources at the local level; and failure to internalize the costs of environmental degradation into the market price of a resource
• Limited availability and transfer of technology, inefficient use of technologies, and inadequate investment in research and development for the technologies of the future
• Failure to manage adequately the use of natural resources and energy.
  

Several environmental issues that traditionally have been viewed as separate are indeed linked with climate change via common biogeochemical and socio-economic processes.