The principal bench of the National Green Tribunal has directed all state governments to undertake carrying capacity (CC) studies of all eco-sensitive zones in terms of air, water, habitat, biodiversity, land, noise and tourism. This is because these zones have been created to act as “shock absorbers” for protected areas.

As a follow up action, one rapid environmental CC study was done for the eco-sensitive zone of Sanjay Gandhi National Park in Mumbai. Later, the green tribunal got a CC study conducted for eco-sensitive and geographical fragile areas of Manali and McLeodganj. Based on the analysis of environmental attributes, it was inferred that parameters such as land use, air pollution, AOD, PM2.5, and noise might be under environmental pressure while other factors such as biomass, forest, NDVI, NDWI fared comparatively better. Now the question of how much public use can ultimately be accommodated in a national park or any eco-sensitive zone must be defined in terms of the CC.

Negative effects of tourism development in a destination are usually the consequence of a high concentration of tourists, accommodation facilities and the activities that are practiced in a relatively restricted area. One of the most important measures to protect the areas is to calculate the maximum number of tourists that can simultaneously reside in a region, vehicles that can be permitted and sport activities that can be allowed. This is the determination of the CC.

The latest definitions of CC for protected areas, such as national parks, fragile ecosystem and wilderness areas, centre on the acceptability of natural resources and human impacts of visitation considering the biophysical characteristics of a protected area (soils, topography and vegetation), social factors (location and mode of travel, season of use, group size, and behavior of visitors), and management policies (visitor use restrictions). These are more important determinants of CC than the number of visitors.

It is true that good progress has been made in evaluating CC, but in many cases the methods adopted for evaluating CC are non-quantitative and lack analytical rigor, whereas CC decisions would be easier if based on the quantitative method. This method helps decision makers/managers (responsible for protecting eco-sensitive zones) to quantitatively determine whether the current state of the target ecosystem is in compliance with established standards for CC. Where it is not, management action can be framed to bring the ecosystem into compliance with those standards.

It is pertinent to mention here that evaluating CC of only protected areas/eco-sensitive zones will not be very effective because the high ecological pressure in urban areas and changing land-use patterns caused by advancing modern lifestyles would have indirect influence on protected areas as cities get close to these ecosensitive zones as they continue to experience population expansion, consumption growth, resource overuse, waste and emission accumulation and many more. Therefore, the most important task is to evaluate the CC of cities that are already non-compliant.

The concept of carrying capacity is widely discounted, in part because it is fluid and virtually unquantifiable. Past discoveries and technological breakthroughs have, many times, raised carrying capacity, and Western science encourages the belief that technology’s potential is unlimited. Technological optimists typically reject scientific warnings that no substitutes exist for topsoil, fresh water, clean air, and the “free services” of many species, or that technology and its deployment to replace existing uses of petrochemical energy will take 20 years to bring about.

Though there is tremendous advancement of science and technology, human beings consistently rely on natural resources for survival and living. Expansive urbanization associated with rapid industrialization causes enormous pressure on the Earth’s resources, and humans’ requirements for resources have surpassed the planet’s regeneration capacity since the 1970s. Thus, it is essential to determine urban carrying capacity (UCC) to ensure the safety of ecosystems and their sustainable development, or at least to slow down the degradation of natural capital.

Environmental and socio-economic factors coexist with each other to support urban sustainable development. On the one hand, the economic foundation promotes social progress, and provides the technological instrument and material foundation necessary for the development and utilization of resources and the environment. On the other hand, resources and the environment provide production and living materials necessary for the development of economic and social activities, and absorb waste products.

Exploring the mechanism of internal interaction between environmental and socio-economic factors is considered helpful to diagnose and compensate the shortcomings of the UCC framework and to construct an early-warning mechanism. In addition, such analysis would be helpful in optimizing the allocation of resources, as well as the environmental, economic, societal, transportation, and other factors. In this way, the coupling and coordination of each city’s CC could be promoted, and regionally coordinated development realised.

UCC analysis helps measure the interaction between human activities and the urban resources environment system and provides foundational knowledge of sustainability, vulnerability, and resilience of land use while addressing issues related to landcover and land-use changes for the purpose of human welfare. Relationships are supported by means of information flow, capital flow, material flow, and energy flow.

For this purpose, the emergent need is to develop research variables (or “carriers” in the present context), methods, and approaches regarding the construction and evaluation of a comprehensive UCC index system against various backdrops. Carriers are water, land , environmental, ecological, social, economical, transportation, resource, and human CC. An appropriate technique is to be employed to examine the dynamic relationship between the carrying capacities. Researchers have already constructed an urban comprehensive CC index in different cities of the world and their findings reveal that transportation carrying capacity was the most important driving force among the other subsystems that interact with each other. Also Land- Cover and Land-Use Change Programme was designed to improve the understanding of human interactions with the environment

In recent years, there has been lot of discussion concerning the carrying capacity of the earth for humans, and the ultimate limit to global carrying capacity for economic development. Thereby a measurement of comprehensive urban carrying capacity (UCC) levels is needed as it is “an important barometer and yardstick of sustainable urban development”. As a follow up action, at least one city , which is the most economically dynamic and institutionally innovative region in India, must be considered to evaluate the UCC levels and dynamic effects of that city area.

The writer is former Senior Scientist, Central Pollution Control Board