A beaver dam

Sustainability can seem like a complicated subject. It’s politically divisive. It challenges our lifestyles. And it’s also based on a combination of different kinds of science. It has one keyword, ecosystem, that most people don’t use a lot. I thought it would be helpful to look at some ecosystem basics.

The “eco” in ecosystem is the same root as “ecology” or “economics.” It means habitat or household.

A system comprising a habitat or household is a set of components related to that habitat or household. They are arranged in such a way that they work together to accomplish some purpose. As far as the root meaning of the word goes, an ecosystem could be a house, the people in it, their pets and houseplants, other living things (bugs, germs, whatever) along with the electricity, plumbing, and other systems built into the house. 

No one uses “ecosystem” that way, but the house analogy has some important concepts that directly help us understand the usual meaning of the term. It includes both living and non-living things. It comprises everything present. The proper functioning of systems in the house depends things outside the system. The weather, for example, or an accident that knocks over a power pole.

Basic components of an ecosystem.

An ecosystem has two main parts, living and non-living. The living parts can be divided into three major components.

• Producers occupy the bottom of the food chain. They use sunlight to convert carbon dioxide and oxygen into simple sugars. They include plants from photosynthetic bacteria to trees. They take in carbon dioxide and release oxygen.
• Consumers, higher up on the food chain, obtain energy by eating other organisms. Herbivores eat plants. Carnivores eat other animals. Omnivores eat both. Most consumers, therefore, are animals. A few carnivorous plants exist.
• Decomposers eat animal wastes and anything that has died. In the process, their own excrement returns nutrients to the soil, which nourishes the producers.

Nonliving elements make up the environment in which life takes place. They include water (and whether it’s salt or fresh), air, and the rocks and minerals in the soil. They also include such climate conditions as temperature and amount of rainfall.

Three characteristics of an ecosystem

NASA photograph of Earth

Besides dividing them into basic components, we need to understand ecosystems as a whole.

First, all ecosystems have boundaries. They may be natural boundaries, such as the shoreline that divides a land-based ecosystem from a water-based one. Or they may be arbitrary, such as a one square meter area a scientist chooses to study. At least some of what happens outside these boundaries matters to what happens inside.

Ecosystems can be large. Strictly speaking, the whole earth is an ecosystem, but it has boundaries. Whatever is above the atmosphere or below the layer that contains life is outside the ecosystem.

Ecosystems can also be small. A single batch of rising yeast bread is an ecosystem. A single drop of water is an ecosystem.

Second, ecosystems change. Changes can come from outside the ecosystem. Sunlight comes from outside. So do meteors, cosmic radiation, and other forces that change the earth as an ecosystem.

Or changes can occur inside an ecosystem. As a tree grows, it creates shade where none was before and increases the humidity in the air surrounding it. Over time, evolutionary change takes place. That’s why, so far, one season’s flu vaccine won’t work in the next season. Viruses evolve.

Third, each element of an ecosystem interacts with other elements to cause these changes. The science of ecology attempts to study all these interactions. The concept of sustainability attempts to help everyone see how their activities affect everything else.

Mostly, the system stays in balance. If something upsets the balance, the system eventually collapses. Ecosystems arose, flourished, and ceased to exist long before the dawn of history.

The human element in an ecosystem

The constellation Orion, imaged at left from dark skies, and at right from Orem, Utah comprising about half a million people.

The emergence of humans has inserted some additional complexities. Well before the start of the Industrial Revolution, mankind was clever (and short-sighted) enough to over-hunt an area, use slash and burn agricultural techniques, or otherwise upset the equilibrium in an ecosystem. As we become more technologically advanced, we have become even more disruptive.

For instance, we can now take petroleum, an organic substance,  and turn it into inorganic plastics that cannot decay and return nutrients to the soil for plants to use as energy. Light pollution from our wasteful use of artificial lights makes it impossible to see much starlight in much of the world.

Perhaps the basic problem is that we focus our attention narrowly. Zoologists study animals. Botanists study plants. These fields of study have only limited interest in each other. A farmer uses fertilizers and pesticides to grow crops and may take no interest in what happens to the excesses the crops can’t benefit from. Interdisciplinary studies have come about fairly recently. And only after specialists have learned more and more about less and less.

That’s humanity at its best. Our species harbors all kinds of criminal and antisocial impulses. Some people take pleasure in destruction and harm.

To whatever extent human activity hampers the normal functioning and balance of the natural world, it causes an unsustainable imbalance. If we are clever enough to build technologies that cause problems, we ought to be clever enough to tweak them and make them sustainable. I doubt if our best can ever completely overcome our worst, but we must keep trying.

Sources:
Ecosystem basics / Urban Agroecology [Link no longer works]
Four basic components of an ecosystem / Andrea Becker, Sciencing. April 23, 2018

Photo credits:
Beaver dam. Public domain from Wikimedia Commons
Houseplant. Some rights reserved by Jennifer Vilches.
Earth from space. NASA photo.
Light pollution demo. Public domain from Wikimedia Commons