Transport

There has been a massive proliferation of vehicles, notably cars, but also boats, planes and trains, in the past century and this has been concomitant with the development of road, rail, port and airport infrastructures. At the end of the twentieth century the numbers of vehicles world-wide were increasing at nearly 3% per year, double the rate of population growth. Most of this growth is focussed in the developed countries where there are over 50 vehicles for every 100 people in quite a number of countries, and some 77 vehicles for every 100 people in the USA (AAAS). By contrast there is less that one vehicle per 100 people in many other countries including very large countries such as China and India.

Road building, particularly in rural areas, often brings considerable problems in terms of erosion and sedimentation. Roads into remote or natural landscapes often bring related problems associated with population movement to those same areas and the conversion of these landscapes. Vehicles themselves are major pollutants. In particular they are sources of a large quantity of greenhouse gases and hence a major contributor to climate change. They also produce other pollutants, including particulate carbon and lead. The latter is now considerably reduced as it is being phased out of use in engine fuels. Runoff from roads, particularly in cities, also includes continuous small quantities of hydrocarbons. The majority of vehicles have a very limited lifespan and can therefore also be a contributor to problems of solid waste.

Air transport is currently increasing at about 5% per year, although increasing fuel efficiency means that fuel consumption is closer to 3%. At present IPCC estimates that aviation contributes about 3.5% of greenhouse gas emissions, and that it is twice as polluting as the motor car per passenger kilometre on short-haul flights.