Robbie Andrew

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Human carrying capacity


One approach to assessing sustainability of society is the concept of human carrying capacity, which, generally speaking, is the population that can live sustainably in a given area. More specifically, human carrying capacity is defined in this report as:

the measure of a specified area's ability to support human activity sustainably given aggregate lifestyle and development choices and the means used to achieve these, and is expressed in terms of number of people.

In any assessment of whether society's activities are sustainable the question of limits arises. An activity may be sustainable up to a certain point, beyond which it is no longer sustainable. An example is abstraction of water from a river, where water cannot be withdrawn any faster than it is replenished. However, often these hard limits are not the limits we choose. In the case of river water, limits are generally set at much lower abstraction levels so that a minimum flow is maintained. This reflects other values associated with rivers, but also acknowledges the presence of uncertainty. Critically, if limits cannot be determined then sustainability cannot be assessed.

A core issue of human carrying capacity is that the relationship between population and limits can in many cases be modified by behavioural changes. For example, installation of rain tanks means that more people can live in urban areas without reaching reticulated water supply limits. As another example, if fewer trips in private vehicles are made per person then more people can live in the District at the same overall level of exposure to oil price volatility. Human carrying capacity therefore depends very strongly on how a community chooses to live.

In this report we present a framework for assessing indicators of human carrying capacity. The main steps in this framework are:
  • Identify a list of potential indicators in consultation with the community;
  • For each indicator assess across a range of criteria including existence and nature of limits, dependence on population, relationships to other indicators, and current and potential monitoring.

  • We expect that it will be possible to determine limits for some indicators, and therefore their absolute sustainability could be assessed, while for other indicators only relative sustainability will be assessable.

    Human carrying capacity is a composite indicator. That is, it combines limits to a wide range of activities to result in a single number: the number of people that can be sustained when those activities are taking place. Because of the number and complexity of factors determining sustainability, it is likely that carrying capacity cannot be calculated directly as there is insufficient knowledge and information to undertake such a calculation. In addition, the 'number' shifts constantly, and can be both added to and detracted from by virtue of people's actions. For these, and other reasons, we recommend caution against the use of a composite indicator in this framework.

    Services from the environment to our culture


    The field of ecosystem services describes how we benefit from the environment, including in intangible ways. While there are some established (albeit debated) methods for putting a value on some services, cultural ecosystem services are often placed in the too-hard basket. In this work, Robbie Andrew provides an overview of cultural ES, discussing the difficulties and presenting some potential solutions. Learn more »

    Scenarios of four futures

    conference report

    In support of qualitative scenario work based on four potential futures of New Zealand, Oscar Montes de Oca and colleagues developed a dynamic environment-economy model. The model combines the dynamics of population, labour force, economic growth, and environmental impacts to investigate the potential outcomes of the scenarios. Learn more »

    Loss of high-class agricultural land

    Development of smallholdings in New Zealand has increased in recent years, as people choose to get back to nature or escape the rat race. Robbie Andrew and John Dymond calculate how much of New Zealand’s best agricultural soils have been ‘lost’ to lifestyle blocks, and discuss what is meant by ‘loss’ in this context.Learn more »

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