Apex predators are indicators of environmental health

Biologists study apex predators like killer whales as an indication of the environmental health of an ecosystem. 

I consider myself an environmentalist. I have heard a lot of sneers and jokes about those “tree-huggers” and “animal lovers” who would rather save a bird than eat, rather look at a bunny in the forest than have a road built there to go faster to the next place of interest, rather have a field with nothing on it but bugs and mice than a profitable shopping mall. I have heard environmentalists openly or by implication called a little crazy or mental. Don’t get me wrong — I would not fight every fight just because it is fought under the banner of environmentalism; I carefully pick my battles. The good news is that there are many people out there who will stand up for what they consider important and are willing to spend time and energy preserving what they care for.

Why do we feel compelled to save natural places, animals and plants? Why do we create mini oases around us in the form of gardens, parks, ponds and greenhouses? Why do we set flowers onto our table to brighten our indoor spaces? I think some part of us needs a connection with the natural environment, the creative air of nature. It calms our mind and it gives us a feeling of familiarity and safety, of origin. It just feels right. In other words, fighting for environmental health is good for our mental health.

In every environment there are predators, and there is prey. Again, the term predator is affixed with negative associations like being mean or a murderer. In truth, almost all life forms eat other life forms; in fact, most cannot exist otherwise. It comes down to personal ethics: Is a killer whale “bad” when it kills and eats a whale calf? Is a wolf bad when it kills and eats a reindeer? Is a bird bad when it kills and eats a caterpillar? What about a salmon that eats a candlefish? A jellyfish just lets its tentacles drag through the water without actively hunting. When a small fish swims into them, the fish gets stunned and eaten. The jellyfish does not have a brain to “plan” the trap, so is it even capable of being judged? Who are we to judge animals for their nutritional needs and hunting practices when, as a species, we have caused more destruction than any species since photosynthetic blue-green algae?

Perhaps I need to throw in a little-known fact of geological history: When the first cyanobacteria split a water molecule and released the oxygen bound in it, the greatest extinction event in Earth’s history had begun. Until then, only anaerobic bacteria formed the life forms on this planet. When oxygen entered the atmosphere, most of them died out from exposure to this deadly poison. Some survived by hiding in refugia where no oxygen could reach. That was billions of years ago, and out of the Armageddon of bacteria extinction evolved almost all life as we know it today, using oxygen for metabolic processes.

Back to the point, animals that prey on other animals but are not hunted by anything are called apex predators. Usually, in biology, we apply the term to animals like killer whales or wolves. Humans, with all their handy tools and protections, have made themselves into the biggest apex predators. Biologists study apex predator populations as an indication of the environmental health of an ecosystem. If the top hunters are doing well, it usually means that there is a balance in the ecosystem that allows for a healthy energy flow to sustain the top level of the food pyramid. If the top predators are starving or sickly, it can be an indication that something is out of balance.

Unless an animal is an apex predator, it is prey to someone bigger. Since it is a basic instinct in all life to survive, prey animals have developed many ways in which to maximize their chances of survival. Some run or swim away as quickly as possible, some hide, some camouflage and hope not to be seen, some develop armor or poisons to make themselves difficult or even lethal to eat. Over the long timespans of slow evolution, every trick a prey organism evolves is countered by a new trick their hunter develops in order to be more successful at finding a meal. It is an evolutionary arms race. 

For the stability of an ecosystem, predictability is an important consideration. On a rocky shore you will find a lot of organisms that are sessile (attached). Many of those sea anemones and mussels can live for many years, through storms, freezing cold winters and sweltering hot summers. On a sandy beach you find fewer animals, and when you dive over a shallow and protected area with a muddy bottom, it looks barren, but a grab sample of the sediment reveals many life forms buried in the mud. Of these examples, the sandy beach is the most frequently disturbed ecosystem. Here, waves move the sand with every change of the tide and every change in wind. Every year between summer and winter the entire beach changes shape, and sand gets carried out to sea or deposited onto land. In an unpredictable and fast-changing environment, it is difficult for anyone to settle and live. If the conditions are harsh it may be difficult, but the organisms can find ways to deal with those difficulties. Blue mussels and barnacles, for example, invented the world’s best biological glue to hold on to the rocks.

We live in unpredictable times, and for many people it feels that the sand is shifting constantly under their feet. But I am an optimist by nature, and as the days are getting longer again, I look forward to welcoming the amazing arrival of some of the largest of animals. Birds that have travelled thousands of miles will come back here, gray whales will pass the island on their migration, orcas will stop by on their feeding visits and humpbacks will hang out for the summer, looking like they are just full of joy when breaching fully out of the water. For me, that is the best medicine for environmental health.

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