I’ve always liked food webs and recognizing how extensive a food web can be. It’s more than a chain as most species can consume different prey. NOAA has a good Lake Superior Food Web http://www.glerl.noaa.gov/pubs/brochures/foodweb/LSfoodweb.pdf. I like that the drawing is not generic of fish eats fish but shows species right here in Lake Superior. Before you go to the link can you create a small web of life in Lake Superior? The little guys we can barely see, such as phytoplankton and zooplankton, are vitally important. We don’t have the bigger fish without the little fish. The poster also has the inclusion of several aquatic invasive species which are here in Lake Superior. Are aquatic invasive species an externality occurring in society? I listened to a seminar the other day that referred to aquatic invasive species as genetic pollution. Are we creating this scary problem? What can we do to prevent the spread of aquatic invasive species? http://www.oar.noaa.gov/oceans/t_invasivespecies.html What about invasive species on land?
When putting a new building in what was once a field, more pervious surfaces is added to an area and will lead to run-off. For ways to reduce run-off go to reducerunoff.org. Efforts can be made to reduce the run-off but if none are done then more water will be flowing off the new paved and impervious surface. Good planning can help reduce the effects on places beyond the property. Putting in a rain garden can be part of the solution to handle the water and also bring a beneficial externality of watching butterflies.
Society has benefited from some production of medicines to help us fight off an illness. However, negative externalities arise such as with the amount of extra pharmaceuticals that remain to be disposed of and that the medicines can contaminate waterways as they go right through a treatment plant and some are having effects mimicking hormones. Plasticizers are another source for the chemicals entering waterways and having health effects on aquatic life. With proper disposal there is a cost – to the Police Departments, incinerator, and awareness campaigns to promote proper disposal. http://www.epa.gov/endocrine/ Can you think of any externalities – good or bad - on other topics? There are many local and global situations of decisions and behaviors having additional effects on other people and places.