On a personal note, I love the images of Lake Michigan dunes. As an undergraduate at Michigan State, I did my best to escape every year to explore these enormous white-sand oddities and feel a bit of wonder.
I did not realize at the time that those same dunes had inspired Cowles' theory of ecological succession, beginning with his 1898 dissertation "The Ecological Relations of the Vegetation on the Sand Dunes of Lake Michigan."
In that seminal work, Cowles explained:
"Ecology, therefore, is a study in dynamics. For its most ready application, plants should be found whose tissues and organs are actually changing at the present time in response to varying conditions. Plant formations should be found which are rapidly passing into other types by reason of a changing environment." (3-4)
While I saw the dunes as a wonder-filled getaway, Cowles saw a natural laboratory: "These requirements are met par excellence in a region of sand dunes. Perhaps no topographic form is more unstable than a dune." (4)
The LOC site has some useful background pieces on Cowles and the other ecologists involved. There are also many more photos worth perusing. I enjoy the group shots especially, for what they show about "the field" as a place that is certainly serious, but also quite fun.