Our Future Is Dependent on Wildlife

Michael Slater
5 hours ago
7 min read

A Discussion of Simon Mustoe’s Wildlife in the Balance

Abundant, diverse wildlife creates the conditions for human life on Earth. This thesis animates Simon Mustoe’s Wildlife in the Balance: Why Animals Are Humanity’s Best Hope, published in 2022. Mustoe builds his argument from established concepts in thermodynamics, mathematical biology and ecology, but combines them into a more provocative proposition: that abundant wildlife is a critical part of the planetary system. Wildlife helps capture, process and ultimately dissipate the chemical free energy generated by primary producers, preventing the accumulation of surplus energy that can destabilize Earth’s environment.

Mustoe grounds his argument in thermodynamics. The first law is that the total energy of an isolated system remains constant, meaning energy cannot be created or destroyed, only transformed from one form to another. Earth is not an isolated system. It receives high-temperature, relatively low-entropy solar radiation and returns approximately the same amount of energy to space as lower-temperature, higher-entropy infrared radiation. Along the way, some solar energy is captured by plants (primary producers), which transform it into chemical energy and store it in organic matter.

The chemical energy stored in plant tissue is a form of free energy. Free energy is available to do work. It provides the fuel for movement, chemical synthesis, growth, reproduction and active transport, and can ultimately be released as heat through metabolism or combustion. Through the continuous input of solar radiation and the remarkable phenomenon of photosynthesis, our planet continually generates stores of chemical free energy in organic matter. This energy is essential to life. Mustoe thinks a problem arises when more free energy is produced than ecosystems can process.

When does stored free energy become a problem?

Free energy is the capacity to cause change. Mustoe argues that when primary production generates chemical free energy faster than ecosystems can capture, process and dissipate it, a surplus develops. As that surplus grows, so does the potential for large and rapid changes when the energy is eventually released. Sufficiently large releases can destabilize environmental conditions. This matters because humans and many other animals depend on relatively stable and predictable environments.

This is where the second law of thermodynamics comes into play. It states that energy tends to become more dispersed and less available to do useful work. Photosynthesis pushes locally in the opposite direction by concentrating solar energy as chemical free energy in organic matter. This does not violate the second law, but it creates an apparent tension with it. The chemical free energy captured through photosynthesis must ultimately be transformed and dissipated. The question for Mustoe is how this happens. If free energy accumulates faster than ecosystems can process it, the resulting surplus can eventually be dissipated in ways that cause rapid environmental change. A planetary environment characterized by the unpredictable accumulation and release of large stocks of energy would not provide the stable conditions that humans and many other animals need to survive.

Mustoe points to the Devonian extinction as an example. He attributes the extinction in part to the expansion of land plants and plant-driven processes such as increased weathering and nutrient flows into the oceans. The resulting increase in marine primary production and organic matter contributed to eutrophication and oxygen depletion. Mustoe interprets this as an example of biological production generating more chemical free energy than existing ecosystems could safely process, contributing to environmental changes associated with the extinction of a large share of Earth’s species. The contribution of land plants, if any, to the Devonian extinction is not settled science. Moreover, the causes of the Devonian extinction are more complex than Mustoe acknowledges.

For Mustoe, wildlife provides a solution to the problem of surplus free energy. Through herbivory and predation, animals acquire chemical free energy stored in organic matter and transfer it through food webs, with much of it ultimately dissipated through metabolism as heat. He writes:

It’s not just the amount of food animals eat that matters though; it’s the patterns of connectivity and behavior that millions of birds and other wildlife create, the innumerable pathways and processes, stacked up to a practically infinite level of resilience to the destabilizing effects of the sun’s energy and the unmitigable power of photosynthesizing plants” (96).

More importantly, Mustoe argues that the complexity of trophic networks increases biological activity and, with it, an ecosystem’s capacity to capture and process free energy. Wildlife therefore does not simply eliminate free energy. It incorporates that energy into complex and active biological systems, reducing the potential for destabilizing surpluses to develop.

Where do these ideas come from?

Mustoe draws on work developed over the past century by scientists in several fields, including Alfred J. Lotka, Erwin Schrödinger, Ilya Prigogine, H.T. Odum and, more recently, Jeremy England. Their work connects life to the capture, movement and dissipation of energy and provides much of the intellectual foundation for Mustoe’s argument.

An early step came from Alfred J. Lotka, a mathematical biologist and physical chemist who applied thermodynamics to evolution in the 1920s. Lotka argued that natural selection tends to favor organisms that are better able to capture and use available energy. Over time, this can increase the amount of energy flowing through biological systems. This gives Mustoe an important starting point: evolution can increase biological activity and the capacity of living systems to process energy.

Physicist Erwin Schrödinger approached the relationship between life and energy from another direction. How can living things maintain their organization in a universe governed by the second law of thermodynamics? In his 1944 book What Is Life?, Schrödinger explained that organisms can do this because they are open systems. They maintain order by taking in free energy from their surroundings and returning degraded energy and waste. Earth works in a similar way. It receives relatively low-entropy energy from the Sun and returns higher-entropy energy to space. Life can therefore create and maintain local concentrations of order and free energy without violating the second law. This raises a question that becomes central to Mustoe: what happens to the free energy captured by primary producers as it moves through the larger ecosystem?

Physical chemist Ilya Prigogine helped answer another part of the question. How can organized systems arise and persist when energy naturally tends to become more dispersed? His work on dissipative structures showed that organized systems can exist far from equilibrium as long as energy continues to flow through them. Living organisms are examples. They maintain their organization by taking in free energy, using it to sustain biological activity and ultimately dissipating energy into their surroundings. Prigogine’s important insight is that the flow and dissipation of energy does not simply break down organization. Under the right conditions, it can also help create and maintain it.

Ecologist H.T. Odum took this energy perspective to the scale of ecosystems. He viewed ecosystems as networks organized around the flow of energy. Solar energy captured by primary producers moves through plants, animals and decomposers, supporting biological activity before ultimately being dissipated as heat. As ecosystems develop, increasingly complex networks of organisms create more pathways for capturing, transferring and using available energy. Mustoe builds on this idea but gives wildlife a more central role. Complex animal food webs, he argues, increase an ecosystem’s capacity to process free energy and reduce the potential for destabilizing surpluses to develop.

More recently, physicist Jeremy England has explored how energy flow may contribute to the formation of organized systems. His work shows that, under some conditions, matter exposed to a continuous supply of energy can become organized in ways that more effectively absorb and dissipate that energy. England’s work does not address wildlife or ecosystems directly. But it reinforces an idea that connects these thinkers: the flow and dissipation of energy may help explain how living systems become organized.

Why Abundance Matters

Ecologists commonly describe processes such as predation, fire or erosion as drivers because they influence how environmental systems develop and behave. At a more fundamental level, energy gradients and their dissipation also drive physical and biological processes. The second law describes the direction of this change: concentrated forms of energy tend toward more dispersed forms. It does not determine what structures will emerge. But the continuous flow and dissipation of energy helps shape the conditions under which those structures form and persist.

Earth’s atmosphere, climate, organisms and ecosystems have all developed within this continuous flow of energy. They are not simply structures that obey the laws of thermodynamics. Their organization is partly a consequence of the thermodynamic processes operating through the Earth system. Once these structures exist, they also influence how energy moves through the system.

This brings us back to Mustoe. Life has evolved on a planet through which energy is continuously flowing from the Sun and ultimately back into space. Organisms and ecosystems developed within that flow and became part of the process by which energy is captured, transferred and dissipated. Mustoe’s concern is what happens as we remove animals from these systems. The loss of wildlife abundance, declining biodiversity and the collapse of trophic networks reduce biological activity and simplify the pathways through which free energy moves. In Mustoe’s argument, this reduces the capacity of ecosystems to capture and process free energy and increases the potential for destabilizing surpluses to develop. The consequences are therefore larger than the loss of individual species. By reducing wildlife abundance and simplifying food webs, humans may be weakening biological systems that help maintain stable and predictable environmental conditions.

Mustoe writes:

Being able to consume, concentrate and reintroduce energy back into a system, amplifying its availability in the most important places and spreading the benefits out regionally, has enabled animal life on land and in the sea to persist for millions of years. Animals do this at every scale from microscopic to regional and some, like sperm whales, at an almost planetary scale. Whole ecosystems would effectively shut down if it wasn’t for animals transferring, amplifying and concentrating energy, converting it into other forms, moving it around, placing it where and when it matters – and, most importantly, in sufficient bulk for our needs. Without wildlife, the world we need to survive would not exist (137).

For Mustoe, restoring wildlife abundance is not simply about protecting nature. It is necessary to maintain the planetary conditions on which human well-being depends.

Our Future Is Dependent on Wildlife

A Discussion of Simon Mustoe’s Wildlife in the Balance

When does stored free energy become a problem?

Where do these ideas come from?

Why Abundance Matters

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