The web of life

_{|  STORY BY MEGHAN MCMAHON |}

_3/3/2023

We learn from a young age about the circle of life — “The Lion King,” anyone? — and how it’s a critical part of healthy, balanced ecosystems. From life comes death, but from death also comes life.

To understand this circle of life and how all living things are connected, it’s important to understand ecosystems. An ecosystem is a biological community that includes all the living things — plants, animals and more — and non-living things in a particular geographic area, according to the U.S. Environmental Protection Agency.

The living things in an ecosystem are called biotic factors, while the non-living things, like soil, water and rocks, are called abiotic factors, National Geographic reports. Every abiotic and biotic factor within an ecosystem depends on all the other factors, either directly or indirectly. These relationships form the so-called web of life.

Picture a large spider web. If you pull on just one tiny strand of silk in the web, it affects all the other threads. Some may move a lot or even be broken by tugging on just that one thread. Meanwhile, the effects on some other threads may be almost imperceptible, but they are affected nonetheless.

Because ecosystems often don’t have obvious borders or boundaries, they oftentimes overlap, according to the EPA. Consider a stream cutting through a prairie. The stream ecosystem and the prairie ecosystem sit side by side, but they overlap in places. And when floodwaters push the stream out of its banks, the two ecosystems become even more intertwined.

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Within ecosystems are food webs and food chains. A food chain is basically who eats whom or what within an ecosystem, while a food web consists of all the food chains in an ecosystem, according to National Geographic.

The species in a food chain are divided into three categories: producers, consumers and decomposers. Producers make their own food, while consumers eat other organisms and decomposers turn organic waste into inorganic material like soil, according to National Geographic.One example of a basic food chain starts with grass, which makes its own food via the sun and photosynthesis, making it a producer, National Geographic reports. Cottontail rabbits then eat the grass (and other vegetation), making them a consumer. Red foxes then eat the rabbits, so they are another consumer in the food chain.

When the fox dies, its remains that aren’t scavenged will be broken down by bacteria, which are decomposers. The bacteria will return the broken down fox remains to the soil, where it will provide nutrients for grass to grow, starting the cycle anew. This is a basic version of the circle of life.

Many other food chains exist in the same ecosystem as the grass-rabbit-fox food chain, with each organism present in multiple food chains. For example, a coyote might also eat a rabbit, and a deer might feast on the same grass the rabbit eats.

In food webs, all the species are organized into categories called trophic levels. The producers — organisms that make their own food — are the first trophic level, while consumers are organized into the middle trophic levels and decomposers are the last trophic level, where one circle ends and another begins.

Consumers are divided into three groups: primary, secondary and tertiary consumers. The first group, the primary consumers, are the herbivores that eat the producers. The secondary consumers are those animals that eat the herbivores, and the tertiary consumers eat the secondary consumers. Atop each of these levels is the apex predator, the top predator in a food chain. Here in northern Illinois, the coyote is an example of an apex predator. Examples of apex predators in other ecosystems include lions, polar bears and great white sharks, according to Treehugger.

The breadth of a food web is its biomass, which is all the energy in the living organisms in the web, according to National Geographic. Energy flows up in a food chain. The most energy is in the lowest trophic level, with producers making their own energy. The higher the tropic level, the less energy, or biomass, there is.

When organisms within an ecosystem are removed or become too numerous or too few, it upsets the balance of the food web and its food chains. This is also true when species are introduced or make their way into an ecosystem where they do not naturally occur, such as with invasive species.

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This balance is metaphorical, however. In truth, ecosystems are fluid, constantly changing in ways big and small. A road or trail may be built through an ecosystem, and certainly many ecosystems change with the seasons with the migration of some organisms. These changes don’t necessarily render the ecosystem unhealthy or unbalanced.

However, too much change within one food chain or multiple chains in a food web can affect the overall health of the ecosystem. When populations of certain species become either too high or too low, all the species can be affected. Think about the example of the grass-rabbit-fox food chain. If the fox population declines a great deal, the rabbit population would likely increase because there are fewer predators. (Remember, though, that rabbits exist in many food chains and have many predators.) If the rabbit population becomes too high, it could eventually lead to a decline in plant populations, which effects not just the rabbits but all the animals in the ecosystem that rely on them.

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While we don’t think of ourselves as part of the ecosystem, we certainly are, and we can have both positive and negative impacts on the health of the environment all around us. We tend to think of our negative impacts — pollution, deforestation, land development — but because of our industrious nature we can affect positive change as well.

Humans consume resources just like other species do, but we also have the ability to make choices to lessen our impacts, something other species can’t do. You can reduce your footprint in many ways, and educating yourself about the value of our natural resources and the health of our ecosystems is a place to start.

Some actionable steps you can take around your house include being mindful of how much water and electricity you use and cutting back where possible, committing to using less chemicals in your home and yard, planting a tree in your yard and choosing sustainable and locally grown foods, according to the National Oceanic and Atmospheric Administration.

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