Ed Golson Outdoor Education

Those crazy humans

Nature tries to keep a balance between all the living and non-living things that occupy the earth. Most of the changes in the environment are gradual and slow enough to allow living things to adapt. The early humans didn't have much effect on altering the world.  There were many fewer people, than today, who lived a life that was in harmony with nature. 

Over time, the human population has increased.  Humans developed technology.  Both of these can have surprising effects on the environment.  They can be positive and negative.   Some of our effects have been very obvious; other effects are more subtle and harder to notice. 

As the world began to fill with more humans, we spread out to find new places to live. Land that once supported wildlife became areas for new cities and suburbs. The increasing populations of humans needed more and more places to live as the old cities became crowded.  What happens to the plants and animals that once lived there?  Are there solutions to help maintain a balance in nature?


Humans have invented many chemicals for the purpose of improving our lives.  They might be in the form of pesticides, and industrial chemicals. Sometimes these chemicals get into the environment where they were not intended to be.  Sometimes humans did not completely understand the consequences of introducing a new chemical into the environment.  Both of these can cause serious problems for organisms that live in that ecosystem. If the problem is left untreated,  the only types of organisms that can survive are the ones that can tolerate the highest amount of pollution. This leads to decreased biodiversity which can alter the food web and make the entire ecosystem less stable. It doesn't always have to be huge amounts of chemicals to cause a change.  Low levels of harmful chemicals over a long period of time can make many organisms sick.  

Another problem with many chemicals is that they may take a very long time to become non-harmful to the environment.  Instead what may happen is that they get passed up the food web as they get eaten. A classic example of this happened with the pesticide DDT. Farmers used DDT to kill insects on the plants in their fields.  When it rained chemicals from the land and air were washed into the water.  The DDT was carried downstream by rivers and creeks into lakes, rivers, etc. Contaminants can get into fish in a variety of ways.  Fish absorb pesticides from either water, suspended sediments, or their food. A small fish became contaminated with the pesticide.  A bigger fish then ate many smaller fish and would end up with much higher amounts of DDT.  If an eagle or other predator ate several larger fish, the amount of DDT would get dangerously high. The egg shells of the bald eagle's young became thin and the eggs broke before they were ready to hatch, causing fewer and fewer baby eagles to be hatched. This became a threat for the bald eagle population.  This process of passing along chemicals up the food chain faster than it can decompose is call bioaccumulation. 

Chemicals like fertilizer are designed to make plants bigger and stronger.  Who doesn't want a nice green lawn with no weeds?   At first, the fertilizer may be a good thing as it helps more plants and algae grow to provide more food and shelter for fish.  Fertilizers that get into rivers and ponds and makes pond aquatic plants grow faster than they should can become a problem.  If nothing is done to prevent the fertilizer from entering the water, the pond will become overgrown with plants. The surface of the water will be covered with a thick film of algae or duckweed.  Many fish may die if they get pushed out of their habitat by the plants. 

Things will get worse as the plants in the pond get old and begin to die. The bacteria that cause the dead plants to decompose use up a lot of the oxygen from the water. Normally the water is able to dissolve enough oxygen from the air to keep up, but when too many plants start dying at once, the water can't keep up. Eventually, there will be almost no oxygen in the water at all. All the fish and other aquatic animals will die off. The bottom of the pond will fill up with a thick sludge made from all of the decomposing organic material. This process of fertilizers causing excess plant growth and eventual death to aquatic habitats is called eutrophication .  

Purple loosestrife in wetlandSometimes we spread invasive species without knowing it, such as when we transfer water in the ballast tanks of ocean going ships, or bring a plant to our area, that is not a native species.  Gardeners can cause problems when they plant a pretty flower from a different part of the world without thinking about the possible consequences.  However, once invasive species get here, they can cause serious problems in our environment. Some reproduce so quickly that they push native species out of their normal habitats. Others simply use defenseless native species as food. To learn more about invasive species, check out our pages on invasive plants and invasive animals .  

For many years, we believed it was best to do whatever we could to prevent forest fires and to quickly put out any that did start . We have now learned that forest fires may only appear destructive, but they can actually play an important environmental role in some areas. Fires can help by opening up spaces in the forest canopy and by helping to get rid of debris on the forest floor. This allows many smaller plants to get the sunlight they need to grow when they would normally be shaded out by the taller trees. Trees, such as the Jack Pine need fire to open their pine cones and spread their seeds, which easily take hold in the newly burned ground below.  Also, the Kirtland's Warbler needs young jack pine forests to breed.  They will not reproduce in an old growth forest. The fire actually creates the new growth needed for this special bird to thrive.  Many plants and animals can only exist in areas where fires are common. If we suppress every fire, we keep these types of organisms from having the type of habitat that they need. This leads to decreased biodiversity which makes the environment less stable. 

Allowing smaller fires to naturally burn also prevents larger, uncontrollable fires from occurring. Smaller fires usually burn dead plants and a few of the smaller trees. Most of the larger trees are spared because small fires can't get hot enough to burn living trees. When we put out all the smaller fires before they can get going, it prevents the dead plants from getting burned up. That means that over the years, more and more fuel for the fires will be stacking up in the forests. When eventually a fire does get started that we can't put out right away, it then has much more fuel to burn. This allows the fire to get much hotter than it would have, which causes many more trees to burn.   Instead of having beneficial smaller fires go through and open up spaces in the forest, we are left with a single large fire that kills off most everything.  

One thing is for certain, humans do impact the environment.  We need to think about if our impact will be positive or not.  We have a responsibility to make sure that we do everything we can to minimize the negative affects of our actions to ensure a healthy environment for years to come.

Back to Previous Page