Biodiversity + Rainfall + Correlation


Image courtesy NOAA

Image courtesy NatureServe

What’s the connection between the South Valley in Albuquerque, and South America?   Biodiversity and water.

I teach a course that combines Environmental Science and Statistics.   We have been working with the US Fish and Wildlife to help develop land that was previously a dairy farm, then alfalfa farm, into an urban wildlife refuge, the Valle de Oro.

As part of the site plan for the refuge, the FWS plans on deploying water previously used to irrigate crops to help create intermittent wetlands, which should bring in both plants and animals not recently seen there…so we should see an increase in the biodiversity.    This won’t be too hard, since the fields have been dominated by the monoculture of alfalfa.

Students are exploring whether it is worth it to devote water to the land, and create the refuge.   To help them make the connection between biodiversity and water (which, to be sure, it pretty intuitive), I gave them this assignment:

Submit a spreadsheet that has:
1) Data for rainfall and associated biodiversity from the two maps.  You should have at least 8 pairs.  Here are some instructions (please listen with headphones) to collect your data from the two maps and place onto excel.
2) A plot of the two sets of data
3)  A cell identified as the correlation, with the correlation coefficient calculated for your data set.
4) A discussion of the relationship between rainfall and biodiversity, which includes in interpretation of the sign and value of the correlation coefficient.

You’ll see that the two maps are the same depicted at the top of this blog.

I got nice response from the students, and because each student chose a different set of locations, each graph was unique.    To wit, here are some screen shots of some student work:

Student 1: “Bob”

Student 2:  “Sally”

Notice that “Sally” had concern over her results: she thought that there should have been a positive correlation, like Bob’s.   The only way I could assuage her concern was to assure her that we would coalesce the entire class’s data, and create a super graph.   In fact, students had to do the assignment twice, but this time with the data gathered from all of their classmates, making the results so much more interesting.

“Frank’s” results, with whole-class data

And with this result came the resolution to Sally’s concern.  Despite the disparities between hers’ and her classmates’ results, when all the data was collected, the final work showed exactly what she anticipated:  more water is associated with greater biodiversity.

Now the students are better equipped to convince others that the Valle de Oro, and New Mexico, will benefit from the use of the water, and can back up their claims with solid data from other parts of the world.

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