Ecosystems are naturally sustainable and a good model for human societies hoping to become more sustainable.

Unlike their counterparts in Greenland, the Icelandic Vikings responded to their environment and adopted more sustainable practices. They didn’t have to look far for a model of sustainability: Natural ecosystems are sustainable. This means they use resources—namely, energy and matter—in a way that ensures that those resources continue to be available.

sustainable

A method of using resources in such a way that we can continue to use them indefinitely.

To survive, organisms need a constant, dependable source of energy. But as energy passes from one part of an ecosystem to the next, the usable amount declines; therefore, new inputs of energy are always needed. A sustainable ecosystem is one that makes the most of renewable energy— energy that comes from an infinitely available or easily replenished source. For almost all natural ecosystems, that energy source is the Sun. Photosynthetic organisms such as plants trap solar energy and convert it to a form that they can readily use or that can be passed up the food chain to other organisms.

renewable energy

Energy that comes from an infinitely available or easily replenished source.

KEY CONCEPT 1.5

Natural ecosystems are sustainable because of the way they acquire energy, use matter, control population sizes, and depend on local biodiversity to meet these needs.

Unlike energy, matter (anything that has mass and takes up space) can be recycled and reused indefinitely; the key is not using it faster than it is recycled. Naturally sustainable ecosystems waste nothing; they recycle matter so that the waste from one organism ultimately becomes a resource for another. They also keep populations in check so that the resources are not overused and there is enough food, water, and shelter for all.

Finally, sustainable ecosystems depend on local biodiversity (the variety of species present) to perform many of the jobs just mentioned; different species have different ways of trapping and using energy and matter, the net result of which boosts productivity and efficiency (see Chapter 8). And predators, parasites, and competitors serve as natural population checks. INFOGRAPHIC 1.5

biodiversity

The variety of species on Earth.

FOUR CHARACTERISTICS OF A SUSTAINABLE ECOSYSTEM

Ecosystems found on Earth today have the capacity to be naturally sustainable—those that were not died out long ago. They all share characteristics that allow the capture of energy and use of matter in a way that allows them to persist over time, all without degrading the environment itself.

Identify an example of each of these sustainability characteristics from the ecosystem where you live.

Answers will vary: For example, consider the temperate deciduous forest ecosystem found in the Smoky Mountains. Solar energy will be the energy source for all plants that live here. (This answer should be the same for all ecosystems - no one lives in deep sea vents where chemosynthesis replaces photosynthesis!) Matter is recycled by fungi which break down dead organisms such as trees that have fallen; earthworms feed on organic matter in the soil; rabbits, mice, squirrels, deer and insects eat plant material; snakes, birds and small mammals eat the rabbits, mice and squirrels (and each other), and so on. Predators like hawks and owls keep the small mammal and bird populations in check; herbivores like the deer keep the plant populations in check. A wide variety of plants are found in different parts of the forest, each able to live in different soil, light, temperature, and moisture conditions. This maximizes the amount of solar energy captured and nutrients accessed from the soil.

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KEY CONCEPT 1.6

Human societies can become more sustainable by mimicking the way natural ecosystems operate.

Thus, natural ecosystems live within their means, and each organism contributes to the ecosystem’s overall function. This is not to imply that natural ecosystems are perfect places of total harmony, but those that are sustainable meet all four of these characteristics.

Human ecosystems are another story. Humans tend to rely on nonrenewable resources—those whose supply is finite or is not replenished in a timely fashion. The most obvious example of this is our reliance on fossil fuels such as coal, natural gas, and petroleum, culled from deep within Earth, to power our society. Fossil fuels are replenished only over vast geologic time—far too slowly to keep pace with our rampant consumption of them. On top of that, we have a hard time keeping our population under control, despite (or maybe because of) all the advances of modern technology. We also generate volumes of waste, much of it toxic, and have yet to fully master the art of recycling.

nonrenewable resources

Resources whose supply is finite or not replenished in a timely fashion.

Increasingly, however, we humans are looking to nature to help us learn how to change our ways. In Janine Benyus’ book Biomimicry (the term used to describe the strategy of mimicking nature), Benyus explains that biomimicry involves using nature as a model, mentor, and measure for our own systems. Emulating nature (nature as model) gives us an example of what to do; it can also teach us how to do it (nature as mentor) and the level of response that is appropriate (nature as measure). As we’ll see in later chapters, scientists are using biomimicry to design more sustainable methods of growing crops and livestock for human consumption, and of trapping and using energy. INFOGRAPHIC 1.6

SUSTAINABLE ECOSYSTEMS CAN BE A USEFUL MODEL FOR HUMAN SOCIETIES

What obstacles stand in society’s way in pursuing the actions mentioned in this graphic?

Some obstacles that stand in our way are economic (some of these actions are expensive to start up, even if in the long term they save money); politics can get in the way of wise long term choices if short term options please more people (or the groups with more political clout); some actions may conflict with cultural norms or religious beliefs (i.e. birth control to curb population growth); technology may not yet be sufficient to meet our needs; the logistics of implementing solutions may be complex (i.e. restructuring the electrical grid or installing charging stations for electric vehicles across the country).

Despite such efforts, some concerned scientists and environmentalists say that modern global societies are not acting nearly as quickly as they could or should. Once again, the charge echoes those that archaeologists have leveled at the Vikings of Greenland. To understand what prevents us from changing our ways even in the face of brewing calamity, it helps to understand why the Greenland Vikings failed to do the same.

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