Necessary constraint

The principal bench of the National Green Tribunal has directed all state governments to undertake carrying capacity (CC) study of all eco-sensitive zones in terms of air, water, habitat, biodiversity, land, noise and tourism because these zones have been created to act as "shock absorbers" for protected areas. As a follow-up action, a rapid environmental CC study was done for the eco-sensitive zone of Sanjay Gandhi National Park in Mumbai. Later, the tribunal conducted a CC study for eco-sensitive and geographically fragile areas of Manali and McLeodganj. It was inferred from the analysis of environmental attributes 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 were comparatively better. The extent of public use that can ultimately be accommodated in a national park or any eco-sensitive zone must be defined in terms of CC.

Negative effects of tourism development arise from the high concentration of tourists, accommodation facilities and the activities that are practised in relatively restricted areas. One of the most important measures to protect these areas is to put a cap on the number of tourists, vehicles and sports activities that can be allowed.

The latest definition of CC for protected areas is centred on the retaining ability of natural resources and human impact, 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 behaviour of visitors), and management policies (visitor use restrictions) to be more important determinants of CC than the number of visitors. Good progress has indeed been made in evaluating CC, but in many cases, the methods adopted for evaluating CC are non-quantitative and lack analytical rigour. The quantitative method helps decision makers/managers (responsible to protect eco-sensitive zones) to determine whether the current state of the target ecosystem complies with established standards for CC. Where it is not, the management action can be framed to bring the ecosystem into compliance with those standards. It is pertinent to mention here that restricted evaluation of CC in 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 lifestyle would have an indirect influence on protected areas. The cities close to these eco-sensitive zones continue to experience population expansion, consumption growth, resource overuse, waste and emission accumulation etc. Therefore, the most important task is to evaluate the CC of cities that are not in compliance with the standards.

The concept of carrying capacity is widely discounted, partly because it is abstract. Past discoveries and technological breakthroughs have, many times, affected carrying capacity. Western science encourages the belief that technology's potential is unlimited. Technological optimists tend to ignore scientific warnings that no substitute exists for topsoil, freshwater, clean air, and the "free services" of many species, or that technology and its deployment to replace existing uses of petrochemical energy will take a minimum of 20 years.

Though there is a tremendous advancement in science and technology, human beings consistently rely on natural resources for survival and living. Expansive urbanisation associated with rapid industrialisation 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 technological instruments 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 interaction between environmental and socio-economic factors is considered helpful in diagnosing and compensating the shortcomings of the UCC framework and to construct an early-warning mechanism. Also, such analysis would help optimise the allocation of resources, as well as the environmental, economic, societal and other factors. In this way, the coupling and coordination of each city's CC could be promoted to realise regional development.

UCC analysis helps measure the interaction between human activities, urban resources and environmental systems and provides foundational knowledge of sustainability, vulnerability, and resilience of land use. It also addresses the issues related to land cover and land-use changes for 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. Carriers include water, land, environment, ecology, society, economy, transportation, resource, and human CC. An appropriate technique is to be employed to examine the dynamic relationships between the carrying capacities. Researchers have already constructed urban comprehensive CC indexes in different cities of the world. Their findings revealed 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 a lot of discussion concerning the carrying capacity of the earth for humans, and the ultimate limit of global carrying capacity for economic development. Thereby a measurement of comprehensive urban carrying capacity (UCC) levels is needed as it is "an important yardstick of sustainable urban development".

The writer is a former Senior Scientist, Central Pollution Control Board. Views expressed are personal