Ecosystems

Last night I went to a Master Naturalist meeting at Springbrook Nature Center.  Our speaker talked about ecosystems.  He asked, "What do you see when you look out the window?"  We see some trees.  "I see a war to the death out there!" says out speaker.  Plants are competing for the best space, the most sunlight, the better chance to grow and crowd the other species out to wither.  Okay, I think to myself, I hadn't thought of it that way before but from now on I will look at the black walnut tree at my front door more suspiciously. After all it is dropping a substance that poisons most other plants.  Only astilbe and lily of the valley can live under it's branches and maybe they would be more vigorous if it weren't for that murderous walnut tree.  I just love speakers with enthusiasm and this guy had it in spades.  We talked about relationships in ecosystems such as mutualism, parasitic, predatory , competition, and commensalism.  He talked about food chains and food webs.  He said the only reason the subcontinent of India can sustain so many people is that most of them are vegetarians.  Beef is high up on the food chain and takes more energy than other foods. But there is no reason to feel smug if your protein comes from soy because acres of rainforest in Brazil are being cleared for growing soybeans.  The food chain, he said, is all about energy.  My mind wandered to the hour I spent in the gym earlier today trying to burn off the energy that I took in today.  How messed up is that?  He ended our talk with a discussion of how the reintroduction of wolves into Yellowstone National Park affected that ecosystem.  When the wolves were reintroduced in 1994, water quality went up rather quickly.  Ecologists were puzzled to see the beaver population increase because wolves eat beaver.  The whole story is incredibly complicated.  The elk, when they weren't worried about being eaten by wolves, hung out near the streams where the tastiest grass grows.  The elk also ate the alder, the willow and the cottonwoods.  This caused the water to flow faster making it impossible for frog eggs and fish eggs to hatch.  Without the frogs and the fish and the river bank saplings, some bird species and beaver left.   When an elk did what an elk has to do that impacted the water quality.  Without the beaver to fell trees the water flowed even faster making for more sediment in the water and again it was harder for the fish to survive.  Now we have fewer species of birds, fish and plants.  The entire ecosystem was out of balance without the top layer of predator.  I am  not describing it as well as he did but I came out of there with a better understanding of what went on at Yellowstone and why it is so important that we keep top predators around.  He went on to talk about Minnesota.  We pride ourselves on our nature and our lakes and our trees.  But none of us living now know what it was like before the loggers took all of the white pine. Two hundred years ago tall, majestic white pines dominated the landscape north of Mille Lacs.  They're all gone.  We've never seen them.  Ecology is a science that is in it's infancy.  In 1902 we knew more about the molecular structure of the atom than we did about ecology.  Those loggers did not know the devastation they were creating.  These guys were trying to make a living and feed their families.  They had no idea they changed the landscape of the state forever.  I love these kinds of meetings where I go home with new ideas swirling around in that cranium of mine, looking at things in a new way.