Carrying capacity assessment estimates the maximum number of people that an area of land can support. A satisfactory carrying capacity model would thus need to encapsulate sufficient aspects of land-usage that impinge on population maximums. This section looks at various carrying capacity assessment models and considers their scale of analysis as well as the insights that they have provided.
Within carrying capacity literature, minor variations exist in the manner to best arrange the physical and sociological components of a carrying capacity model, but generally, they encapsulate similar fundamentals. For example, Fearnside[5] cites population, a particular area, environmental degradation plus a combination of technology and consumptive habits; House and Williams[6] propose resource production, environmental assimilation, infrastructure delivery and quality of life concerns; Thurow[7] profers production, consumption, egalitarianism and social discipline; while Hardin[8] reduces resources and lifestyle to a concept of cultural carrying capacity. Despite these differences, most authors define the limits to population by either their required inputs or subsequent outputs. Whether these inputs and outputs are culturally, technologically, economically or physically determined, they still form the basic determinants of carrying capacity. So, in essence, resources form the limiting factor on the input or supply side of the equation while environmental impacts form the opposing carrying capacity barrier on the output side. The population is wedged between these barriers but can alter the demands of each by collectively altering its behaviour.
An assessment of current carrying capacity literature suggests that methodologies can be categorised into approaches that focus more or less on the various components of a basic carrying capacity model (Figure 11). These elements include global boundaries, local boundaries, resources, population and impacts. Ultimately global limits form the outermost boundary for humanity’s carrying capacity. However, this level of analysis may not be the most appropriate scale for measuring population carrying capacity. Many authors subscribe to more localised boundary delineation within which to define smaller populations.
Figure 11. Carrying capacity modelling can be encapsulated in a simple input-output diagram. Resource inputs and impact outputs are positioned both within local and global boundaries as they can potentially occur at both scales. As Durham[10] points out, “[l]imits exist in both the resource and sink functions of the environment.”
