Degradation and extreme alterations to the natural environment pose some of the deepest challenges to modern society (Vitousek et al. 1997). The effects of humans on the planet can be found everywhere, from the interstices of the polar ice caps to the depths of the oceans. Although many governments and institutions have accepted that action must be taken to tackle the most urgent problems, increasing levels of consumerism and the inexorable drive to improve the living conditions of people in the developing world mean that society is being pushed up against a wide range of environmental limits. This is the challenge facing sustainable development.
The sheer scale of the flow of materials from nature to society and back is remarkable: Even in the most modern and efficient industrial economies, the average per capita consumption is 60,000 kg of natural resources per year, the weekly equivalent of 300 shopping bags filled with materials, or the weight of a luxury car. Given population growth, resource use will have to become much more efficient by 2030 just to keep environmental degradation at present levels (Daly 1997; McGlade 2002).
What can also be observed in many parts of the world is that through our ability to manipulate and alter the fundamental relationships underpinning the planet's ecosystems, we have begun to expose ourselves to a variety of gradual and unexpected ecological changes leading to the loss, severe decline, and shifts in the ecosystem services on which we rely (Gewin 2002; Ayensu et al. 1999; Millennium Ecosystem Assessment 2003; EEA 2004).
There is a growing body of evidence from many bioregions that the accumulation of small, seemingly insignificant changes can lead to greenlash: flips or dramatic shifts in the structure and dynamic behavior of ecosystems (Rand et al. 1994; McGlade 1999). Greenlash can happen without warning; sometimes this is because we inadvertently lose a set of functional relationships or keystone species, which hold together networks of feeding relationships, because they are geographically distant or hidden within trophic dynamics (Hogg et al. 1989). It has also been observed that the removal or loss of keystone species can cause irreversible changes. This was noted in Paine's early work (1974) and in many other areas. For example, in lakes (Carpenter et al. 1985) and the Sea of Azov, large-scale hydrographic changes caused by increased use of freshwater from rivers for domestic, industrial, and agricultural purposes led to significant increases in salinity, which caused the loss of the key planktonic food items for the major fish species and the collapse of many fisheries (Mee 2001).
Many changes can occur without early warning signals. Changes in climate, levels of toxic chemicals, habitat fragmentation, and loss of biodiversity often appear to occur gradually, but ecosystem responses can be striking and sudden. Predicting which types of change will occur and over what time and space scales is fundamental to protecting our environment. Sentinel indicators—those that capture the dynamics of change—are essential in this context and may not coincide with any keystone species.
Detecting Changes on Different Time and Space Scales
Ecosystems have different levels of resilience, resistance, and hysteresis. Long-term data series can help predict which responses are most likely to occur, but often it is phenomena at the margins or on local scales that give us the clues. Changes in local conditions can result in local extinctions for certain species, but in most instances their loss is rapidly made up by surrogates. However, in some instances declines in species affected by long-range processes may not always be so easy to detect (Keeling et al. 1997; McGlade 1999).
Environmental degradation and changes such as global warming, the depletion of the ozone layer, and the presence of toxic polychlorinated biphenyls in Antarctica have arisen because of activities within national boundaries, often thousands of miles away, and a misdirected sense of concreteness in overall policy thinking.
Unfortunately, in many of today's environmental institutions there is still a belief that models coupled with management intervention can lead to predictable outcomes. But well-structured theories are conspicuous by their absence in environmental management, and many of the models used include only a limited number of possible future states. So it is extremely important to understand which indicators can best provide early and maturing signals of change.
The other downside of our false sense of security in interventions is that they very often go wrong: The introduction of rabbits and cane toads and the inadvertent transport of alien species around the world are constant reminders. Unfortunately, such experiences seem to have taught us nothing. It seems that the road to ecological disaster is littered with good intentions.
In the past, environmental decision making was made on an ad hoc basis, solving each particular problem in isolation from others. Now, however, a more profound thinking is needed about production and consumption patterns and how we can support different societies without engendering significant unintended shifts in the biosphere. Laws and institutions, no matter how efficient or well arranged, must be reformed or abolished if they are unresponsive. Overexploitation and misuse of resources must be curtailed or prohibited if they cause fundamental harm to environmental processes, but we need indicators of change to guide us along the way (McGlade 2001).
It is increasingly important for sustainability policies to be supported by information flows from heterogeneous sources. Whether these relate to economic, social, or environmental processes, they will need to be monitored in a transparent way, through electronic transactions across a wide range of communication media.
Indicators represent, at root, an approach designed to meet this challenge. The majority of sustainability indicators are derived from separate analyses of economic, social, and natural processes. In some instances, however, the indicators are integrated across more than one domain. Those charged with delivering sustainability are seeking this connectivity across varying levels of complexity and scale.
A characteristic of indicators is that they allow an expanding set of sentinel observations to be drawn into policymaking. As new knowledge becomes available or the focus of decision making shifts, underpinning data flows can be augmented or replaced. Indicators can be descriptive, related to performance, efficiency, policy effectiveness, or overall welfare, but in the context of sustainability it is their integration across different policy arenas that is most critical.
Perhaps the biggest bottleneck facing us today is our ability to choose the right signal or indicator to make a decision at the right time. What is needed is an indicator framework in which to successfully monitor, learn, decide, and act, to be able to obtain a clear view of where current and proposed policies are taking society.
The main purpose of any sustainability indicator framework is to provide a comprehensive and highly scalable information-driven architecture that is policy relevant and understandable to members of society and will help people decide what to do.
It must contain sentinel indicators, ones that directly reflect changes across significant areas of interest to society and can be communicated easily. In this way we will be able to learn about changes and interpret the various forms of information as clear views of progress to date and possible future directions. In this way we will be able to achieve balance in our actions.
The framework must cover an end-to-end process—monitor, assess and learn, decide, and act—and be transparent throughout. The sustainability indicator frame work calls for a modular approach, allowing new modules to be introduced, taking advantage of core infrastructures, reducing costs, identifying risks, and integrating different processes into the cycle. A modular approach allows continual refinement and improvement even for issues that do not yet warrant a dedicated monitoring solution or have not been anticipated. Throughout each step, the identification of sentinel information, its verification, and the links to policies and other indicators of economic, social, and environmental health must be accessible. Peer review and societal acceptance are key elements in building confidence in the use of sustainability indicators, which in the end must give us a clear view of where policies are taking society.
As is widely recognized, sustainable development must be central to its vision and practice. The objectives of economic prosperity, social well-being, and environmental recovery and protection must be better integrated into our practices and policies.
The enlargement and review of the European Union sustainable development strategy provide a unique opportunity to reinforce sustainable development. At the moment, however, many national sustainable strategies obscure a number of important challenges: how to turn ambitions into actions, how to ensure effective policy coherence, and how to best provide a focus and set priorities. Most strategies have been led by environment ministers and remain silent on how sustainable development priorities are to be integrated into the budgetary process. The strategies often are unclear as to how the costs and benefits of policies, including inaction, across different sectors can be systematically assessed to allow informed decisions to be made. The majority of strategies are too all-embracing and run the risk of poor implementation. A key consideration is how to harness the existing momentum at national and international levels so that they can become mutually reinforcing. The different strategies should define a common vision, encourage the creation and regular updating of information on sustainable development, reinforce progress using relevant indicators, promote leadership for sus-tainability, and create a wider public understanding.
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