Author: Edward. W (Ted) Manning, Ottawa.
The concept of carrying capacity is a valid one, and a useful adjunct to the discussion of limits, particularly in the context of development and growth. (Meadows et.al, 1972). While it may appear a straightforward concept, in practice, however, the reality of carrying capacity is complex, involving many different factors and in fact can alter over time. The assessment of capacity in any ecosystem, community or site must therefore address a range of factors which can affect the success and sustainability of any level or type of development and these are the real limits to growth an any place or time.
The concept of carrying capacity is founded on the experience of pastoral agriculture – where it was observed that a pasture could support in perpetuity a particular number of cattle. If this threshold was exceeded, the supporting system was damaged, often to the point where it could no longer support grazing at all. Carrying capacity measures what level of use is sustainable. However, its initial application was to only one product – the number of cattle which could be fed. In fact, carrying capacity is much more complex, particularly when a very wide range of valued products and services must come from the same environment.
When applied to particular ecosystems or communities the concept of carrying capacity has value, particularly because it draws attention to limits and thresholds. However, in dealing with the reality, we need to consider the following factors:
- Communities depend on many attributes of an environment – resources, aesthetics, maintenance of flora and fauna, access to shoreline, ambience of a community and ability of a site to support active uses (e.g., sports). Each has its own response to different levels of use. Each has its own particular dependence on certain attributes of the ecological and social system. De Groot’s work on environmental functions shows a wide range of dependencies on different aspects of any ecosystem which need to be sustained to support these often competing uses. (DeGroot, 1986)
- The impact of human activity on any ecosystem may be gradual, and may affect different parts of the system at differing rates. While some key functions supported by an ecosystem may have precipitous thresholds (e.g., removal of habitat for fragile or endangered species), others (e.g., water quality) may degrade gradually in response to different use levels. Like ecological systems, social systems may also have sudden thresholds – when the limits of community tolerance are breached.
- All environments are multipurpose environments – the sensitivity of an environment to different use levels depends on the demands and values of all of the users. In one site it may not matter greatly if a river is diverted or a breakwater built. In another, because downstream or further along the coast a community depends on that source or a stream flow for its water or food, or as a critical element in providing suitable habitat for a species to breed, it may be a critical impact.
- Different types of use have different impacts (e.g., 100 persons walking vs 100 on off road vehicles or 10 photographers vs 10 hunters, pastoral agriculture as opposed to cropping). In communities, local residents may have significantly lower impacts than groups of rowdy visitors while local fishers may or may not deplete stocks. Some uses may be compatible with others while some may degrade the utility for other users (e.g. polluting industry relative to fish habitat).
- The values affected by use may also decline gradually without discernable thresholds. How dirty does the water have to be before someone decides not to swim in it or use it for laundry? How dirty before most, or all persons decide the same? Which set of values defines the “carrying capacity” for waste in the water? Whose definition is being used for “drinkable? Are the values of all residents or visitors to the local community the same?
Because of these concerns, when applied to human systems. a simple definition of carrying capacity involving the identification of a single threshold value will be inadequate in nearly all cases. This reinforces the conclusion in this regard contained in the paper 1990 WTO/UNEP workshop on carrying capacity and also in the 2004 Guidebook on Indicators of Sustainable Development for Tourism Destinations, WTO, Madrid). It also reflects some of the caveats contained in work as early as 1980 regarding use limits for activities in sensitive wetland systems. Efforts during the 1980’s to define capacity standards – which suggested using working limits for particular types of human activities in a set of different ecosystems types has led to some practical standards for limits of use but also shown the need to adapt these to the unique conditions of each site.
Sensitivity, Impacts and Limits
Instead of focusing on specific capacity or density calculations, a revised approach to the identification of impacts and of limits is needed, which better reflects the sensitivity of different attributes of the environment to different types and levels of impact or use. This approach, based on the concept of system sensitivity, and also on the use of indicators to identify and measure discrete factors which affect sustainability, is central to the approach proposed. Sensitivity and limits are a better measure than any single capacity measure. The impacts of human use depend on many factors:
- How many
- What they are doing – where and when
- What they expect
- How they are controlled
- The specific sensitivity of the ecological and cultural systems which are used or impacted
- How the impacts are managed
- Whether or not there is mitigation, repair or cleanup.
Because ecosystems are shared with many users, it is seldom feasible to plan only for one sector or use. Instead, integrated regional or community planning which the interest of any specific sector is necessary. The relationship between all users of any ecosystem can be viewed as a complex supply/demand relationship. The environment, based on its biophysical characteristics, is the source of all goods, services, and experiences; it is the base resource on which the ability to satisfy human wants and needs, as well as the needs of other species is founded. The many different attributes of the environment are the basic resources which support habitation in particular parts of the planet. Demands placed on the environment by any sector are cumulative with those made by other sectors, the community, and by plants and animals, and must be considered within that context. Where new uses (tourism, forestry, plantations, mining etc.) are proposed it must be realized that in nearly all cases the ecosystem(s) already support some human use – ranging from intensive urban and semi-urban areas to more rural and remote ones, and most have supported other human activities for some time.
The demands placed on any ecosystem by current and proposed users are based on both the numbers of users and the attitudes and expectations of each – the footprint of each on the place. Each ecological system has the capacity to serve a finite range of demands – and the demands of all users, need to be viewed relative to this ecological capacity, as well as relative to other elements which help define limits and opportunities. This concept is fundamental to how we define carrying capacity – in terms of the needs and wants of all users of ecosystems. Any sector functions as one part of this larger supply/demand relationship.
Defining sustainable options (and capacity and limits) therefore requires a more specific focus – on the measurable attributes of capacity/sensitivity which can be monitored and managed – with indicators as a key management tool. In evaluating any change in human activity capacity depend on all of:
- Ecological Sensitivity
Planners need to understand what the key ecological assets are; and how fragile or sensitive these assets are to different types and levels of use. This leads to the ability to determine the extent to which development or uses can be designed to respect the key sensitivities. It also facilitates understanding of how activities can be managed to eliminate unacceptable impacts, and how to reduce or mitigate negative effects. As well, vulnerability to external factors (climate change, invasive species) needs to be considered.
- Social Sensitivity
Capacity can also be based on cultural assets. Built environments, (forts, villages, religious sites) and cultures (ceremonies, events, costume) are important assets, and can be impacted by any changes positively or negatively. Each has its own sensitivities, affected by the concerns and wishes of the residents, their expectations of an acceptable future, and the degree to which these expectations relate to any proposed alterations. It is critical to understand the values and sensitivities of the community (and indeed all cohorts of the community) and to try to establish what is negotiable, and what is not. One means to address this developed in the tourism industry, is to identify the limits of acceptable change in the eyes of both local residents and those from outside the community who may use its assets. Indicators can help to clarify and measure key aspects of what is valued and by whom, and to what extent these values are impacted by any changes.
- Economic Sensitivity
Economic stability and the capture of benefits are critical factors in overall sustainability. Economic capacity includes many elements (which can affect ability to support any changes or the nature of benefits/disbenefits associated with any proposed changes). These include:
- Ability to fund infrastructure upon which current and potential users depend
- Ability to pay for governance related to changes
- Ability to retain benefits in the community and region.
- Equity issues, participation and sharing – who benefits, and who does not?
- Ability to manage and mitigate any negative economic impacts on the community (price of basic goods, accommodation, access to traditional sources of resources or income, poaching of skilled personnel)
- Ability to assure a stable economic environment for investment
These issues/areas of concern relate to the economic sustainability of a destination and may provide limits/opportunities for sustainable development at many scales.
- Infrastructural Capacity
Infrastructural capacity is often the most easily defined limit and may also be among the easiest to change. Infrastructure may define capacity in the short to medium term. Road capacity, current capacity of a water system, electricity generation utility, or ferry service, number of parking spaces or campsites (or even current number of hotel rooms) is an easily measurable limit – at one point in time. Infrastructural limits are also more easily altered than many other limits or thresholds – although the ability to make the alterations may be closely related to economic capacity, community willingness to allow new infrastructure to be built or old services/infrastructure to be removed, and to the ecological limits which may militate against additional construction. These temporal limits can be measured, as can current use levels (% of capacity of the sewage treatment system now in use).
- Institutional Capacity
A factor which is sometimes missed in the assessment of limits and barriers is institutional capacity. Delivery on projects and the management of assessment itself requires suitable institutions and trained staff. Ability to plan and manage sustainable development and to deliver ongoing management/enforcement/governance can be a limit. Often there may be no organization at the appropriate scale (the destination, community or site) to design, deliver and monitor development. Legal framework (land titles, investment rules, tourism laws, labour, environmental laws etc.) may not be in place, or be enforced. Often existing stakeholders may not be organized and/or able to participate in planning and management. Frequently there is no plan or vision for the place, no clear mandate regarding creation of such. These factors are important to the ability to deliver any form of sustainable development. Human resources can also be a limit, particularly for less developed or more remote places. For example, in several African examples of new development, the local nurse or teacher was hired to be the mine accountant or hotel desk clerk, leaving the community without those services.
Indicators of Sustainability
One means to manage within capacity limits is to identify and monitor specific sensitivities – relative to the ecological, economic, cultural, perceptual and infrastructural factors present or affecting a destination or site, as well as to monitor management capacity relative to the needs. A tool which is particularly useful to help define and measure the key sensitivities in any site is that of indicators. This can also be part of any review process – such as Strategic Environmental assessment (SEA) Environmental impact assessment (EIA), social assessment, rapid urban or rural assessment which occurs in planning.
To be of maximum utility, a limited set of agreed indicators should be used, focusing on:
- Response to the key limits and sensitivities of a community or ecosystem
- Measuring the main risks to the place and to specific initiatives
- Monitoring the impacts of specific activities which have potential impacts on the ecology, society and economy
- Measuring performance with respect to attainment of goals for the proposal and for the entire area involved
The objective is to reduce future risks to the ecological, socio-cultural and economic functions of regions (destinations) to the benefit of all. This relates to carrying capacity because each indicator chosen focuses on the monitoring of trends or changes relative to particular sensitivities, limits or thresholds which together describe carrying capacity for the destination.
|According to the UN World Tourism Organization which has pioneered the use of indicators for impacted ecosystems and tourism destinations, good indicators are : |
· Relevant – to real decisions (such as the decision of what to build, where, how to
design and manage, how to mitigate negative impacts)
· Feasible – practical to obtain (if possible from existing data sources)
· Credible – they are believable to those who will need to make decisions
· Clear – what the indicators show is easily understood
· Comparable – can be used to measure change or benchmark to other sites
(from WTO 2004, Indicators of Sustainable Development for Tourism Destinations: A Guidebook, Madrid
The use of indicators is central to:
- the identification of those factors most critical to the sustainability
- the clear definition of the factors most important as limits and thresholds – which delimit the capacity of any destination to support different types and levels activity at any point in time
- the measurement of change in use and impact relative to any known ecological or infrastructural limits or in terms of limits of acceptable change (social and cultural limits)
- the measurement of performance of any projects or programs affecting an ecosystem, community or site relative to design goals and key sensitivities.
It should be understood that indicators can be used at many scales to support decisions on planning, management, and evaluation – including national, destination and project levels.
In conclusion, the concept of carrying capacity needs to applied within a spatial or geographic framework, include all sectors, and also encompass a range of different elements of sensitivity.
Carrying capacity as a concept works best as a point of reference for sustainability and can help to define the sensitivities which need to be included in any comprehensive planning process.
DeGroot, R.S. 1986, A Functional Ecosystem Evaluation Method as a Tool in Environmental Planning and Decision-making (Wageningen, Netherlands: Nature Conservation Dept., Wageningen Agricultural University)
Hardin, Garett., 1968, “The Tragedy of the Commons,” Garrett Hardin, Science, 162:1243-1248
Manning E.W.(ed), 2004, Indicators of Sustainable Development for Tourism, Madrid, United Nations World Tourism Organization.
Manning E.W. and T.D. Dougherty, Planning Tourism in Sensitive Ecosystems. Tourism Recreation Research, India. 1998.
Manning, E. W., and M. Sweet, 1993. Environmental Evaluation Guidebook: A Practical Means of Relating Biophysical Functions to Socioeconomic Values. Centre for a Sustainable Future, Foundation for International Training Toronto
Meadows D. et. al, 1972, Meadows, D. H.; Meadows, D. L.; Randers, J.; Behrens III, W. W. (1972), The Limits to Growth: a report for the Club of Rome’s project on the predicament of mankind, Universe Books.
Bio: The author, Ted Manning is the President of Tourisk Inc, a full Member of the Club of Rome and former Chair of the Canadian Association for the Club of Rome. A specialist is sustainable development he has worked in more than 50 countries on environmental projects.