Our world is a beautiful and interconnected biosphere that supports so many magnificent forms of life. It is simplistic to describe its workings with a small number of ecological concepts. Yet we all need to grasp the basic ideas so that we can understand the impact of our lifestyles and institutions on other creatures and people, both now and for the future. Various ecologists have organized these basic concepts in different ways covering the same material. We use the concept labels from SunshipTM Earth and call them the Earthworks. We think they do an excellent job of including and organizing the key ideas in a simple and understandable format. We elaborate on these concepts below using practical examples.
- Energy Flow – The sun is the source of energy for all living things.
- Cycles – The building materials of life must be used over and over.
- Diversity – Differences in living things provide for the success of all life.
- Community – Plants and animals live together in areas that meet their special needs.
- Interrelationships – All things interact with other things in their surroundings.
- Change – Everything is becoming something else.
- Adaptation – To survive, everything must fit how and where it lives.
* These principles and their associated concept statements are drawn from SunshipTM Earth by Steve Van Matre, Institute for Earth Education, Cedar Cove, West Virginia, 1980, p. 64-68.
All too often, we think of the sun only as a source of warmth, whether it is on a cold, winter day or an unbearable summer afternoon. Yet those sunlight rays provide all of the energy needed to keep all creatures on this planet alive. Green plants – be they broad-leafed trees, seaweeds, ferns or moss – are the only ones that can capture and turn energy into basic sugars through photosynthesis. These sugars are in turn transformed into other substances and passed along food chains as food energy for all other creatures, be they caterpillars, birds or foxes. Every creature uses this energy to survive and then passes it on in an altered form. The rabbit hops, the plants breathe and we perspire. Energy flows through all living things.
In contrast to energy, the atoms and molecules that make up all materials on earth are limited in quantity. They are constantly cycling through living and non-living things, passing through the air, water and soil. In the air, oxygen and carbon dioxide are connected in a great cycle. The plants produce the oxygen that animals need to breathe while animals give off carbon dioxide that the plants use to make sugars through photosynthesis. Of course, other molecules such as those incorporating nitrogen and sulphur also cycle through the air and have important effects on living things.
The cycling of water is easily visible to us in the form of rain, yet we forget the other phases of this cycle. The rain is filtered through the ground, and purified in the process. Some becomes drinking water for us and for other animals and plants. But much of it filters through to streams, rivers, lakes and the oceans. The heat of the sun then evaporates enormous quantities of water up into the sky off of these bodies of water. The water vapour forms clouds that are swept across the sky by the winds. Ultimately, the water vapour condenses amidst the cooler temperatures at higher altitudes and falls again as rain. Until recently, North Americans took this cycle for granted. Now we are becoming more aware of how our lifestyles are changing the water patterns as we confront climate change.
Materials also cycle through the soil. They are the nutrients (carbon, nitrogen, potassium, etc.) required for the growth of all plants and animals. After plants and animals use them, or die, decomposing creatures break them down and return them to the soil. The cycles move the nutrients around and around to support all life.
“Stand and fill your lungs with air. With every breath you inhale a thousand billion billion atoms. A few million billion of them are long-living argon atoms that are exhaled within a second and dispersed with the winds. Time mixes them and has been mixing them for a long time. Some of them may have visited Buddha or Caesar, or even earlier paid a call in the Man from Makapan.”~ A. Rolf Edberg
Diversity represents the differences in the types of living things and in the types of things they need to survive. Various plants have different needs for light, nutrients and water that allow them to coexist together in one area or inhabit different areas. If all plants required full sun, then the forest floor would be barren. Only some plants can survive in deserts. Diversity enables many forms of plants and animals to live together. It produces a strong interconnected web of relationships that supports all life.
Our lawns and tree plantations are tragic examples of the problems that occur when diversity is lost. Large concentrations of one species (grass or tree) invite attacks from large concentrations of other creatures (a given insect species). The insect ultimately moves on or dies out when its food source is wiped out. The community is left degraded or destroyed because all of the other creatures were dependent on the one dominant plant. In contrast, if many different species live together, the overall community is not threatened if natural events result in the loss of one species.
Specific plants and animals live together in particular areas because the local conditions and mix of plants and animals are mutually beneficial. The boggy coastal barrens of Nova Scotia are well-suited to pitcher plants and low berries precisely because the climate and soils are inhospitable to taller plants that would block the sun. The berries in turn provide a food source for a range of other creatures which live nearby. The result is a group of creatures that live together in a certain place.
“The frog does not drink up the pond in which it lives.”~ Indigenous Proverb
The relationships between all of the creatures in a community are impossible to fully understand or predict and yet so important to the success of life. Ants living in dead trees are a food source for the pileated woodpeckers. The trees also provide a home for the woodpeckers. Yet skunks compete with the birds for the ants, while squirrels may take over the woodpecker holes. The squirrels may in turn store acorns in the holes where blue jays find them. Creatures are implicitly competing or cooperating with each other in a multitude of ways as they seek food, water and shelter. There are enormous numbers of interconnected and crucial relationships.
All creatures and natural communities are changing over time as local conditions change. The disappearance of the dinosaurs, the accumulation of topsoil and the growth of a tree are examples. Major natural changes are typically slow. The dinosaurs disappeared over several million years while it takes nearly a hundred years to create a centimetre of topsoil. In contrast, human-induced changes can be very rapid. Large machines can remove the topsoil in a minute. A pesticide can eliminate a species in an area instantly. Change is natural, yet the pace and magnitude of human changes can be catastrophic for natural communities.
Every living thing has developed a specific set of physical characteristics and behaviours that help it succeed in obtaining food, water and shelter. For instance, there are many different types of butterflies and bees because they have a wide range of means to suck nectar from different flowers. They have adapted their strategies and changed their physical characteristics over time based on what plants are available and what else is competing with them. All creatures adapt at a slow pace to changing conditions. However, rapid human-induced changes often outpace the ability of other organisms to adapt and survive. The caterpillars of monarch butterflies rely on milkweed plants for their food, yet milkweed is diminishing in numbers in some areas because it is sprayed with herbicides. Many farmers view it as a weed when it grows along or in agricultural fields.
These seven ecological concepts broadly define the workings of our earth, although there is an immense depth to them that even the most sophisticated scientists do not understand. But these broad ideas are important in helping us to understand how our lifestyles impact natural communities and how we can change. For example, the cycles concept tells us that the human-synthesized chemicals will never break down, or ever “go away”. They are always moving through the cycles and having an impact in one way or another. Understanding how the earth works can help us live more sustainably.