Current trajectory of human action is not sustainable at a global scale: how can scientific understanding of complex systems and human perturbations devise sustainable development pathways across the scientific, policy and resource management divide, particularly at the regional level where most decisions are taken?

During the last 50 years the human population has risen from to 2,5 to over 6 billion. The use of land, water, minerals and other natural resources has increased almost ten-fold over the last two hundred years and approximately 50% of the ice-free land surface has now been significantly modified by humans and most of the rest is managed for human purposes. This phenomenon, which has obvious implications, creates the need to study the interactions, which occur on different temporal and spatial scales, affecting the biosphere and which are particularly susceptible to human actions, especially the efforts to provide a growing human population with food, energy, shelter and employment.

A global change research perspective which places primary emphasis on the global scale often misses a vast amount of work, frequently done under other guises, which is directly relevant to the study of global change phenomena. Such work is crucial for understanding the underlying processes which when aggregated constitute global change. Ultimately global change research will provide much of the underlying scientific understanding of complex systems and human perturbations that is required to devise sustainable development pathways at regional level. The drive for sustainability – the desire to make the development of the growing ‘human enterprise’ more compatible with the natural evolution of the Earth system – gives global change research its most fundamental rationale and connection to applications in policy and resource management. Where global change research is weak – application of the work through interaction with the policy and resource management sectors, sustainable development science is strong; and where sustainable development work is often weak – understanding the fundamental dynamics of complex environmental systems, global change research is strong. Clearly, the two fields of enquiry should work in much closer harmony in the future.

How can we establish and maintain a sustainable relationship between humans and the rest of the living world?

This is without doubt the most important and challenging question that has ever faced our species.

Our present use of the planet is not sustainable. Achieving “a sustainable relationship between humans and the living world” will require a huge intellectual, scientific, technological and social effort.

Whatever sustainable means, maintaining the current number of humans is not an option, and we cannot continue to extract services from the natural world at the rate we do today. Stopping soil erosion is not enough; nor stopping climate change; nor is stopping the fragmentation of habitats or the damming of rivers. Sustainability is not just a matter of making sure that the rate of use does not exceed the rate of replenishment. We must reverse many trends, overhaul our organisations and the way we do things, and considerably improve the processes we use to grow and prepare food, clothes, and other material goods, and to transport them and us around the place.

If we are to meet this grand challenge one thing is essential: the contribution of science in all its many flavours.

Understanding how to establish and sustain a balanced relationship between humans and the rest of the living world will certainly need reductionist, rational, value-free and quantitative knowledge of the natural world and its interaction with our activities. But it will also require holistic, partly intuitive, ethical and qualitative knowledge, accumulated empirically over a long time and through learning by doing.

Let us direct every effort towards understanding, and increasing the capacity to understand, our living planet as a single, complex entity.

We need many more socio-ecologists out there doing anthro-geo-physiological fieldwork. We also need philosophers and communicators and people who delight in studying and understanding complex, interacting, self-regulating, far-from-equilibrium, self-organising, ambiguous, borderless systems.

Let us learn how to expect the unexpected.