Einar Haugen pioneered a form of linguistics which used the metaphor of an ecosystem to describe the relationships among the diverse forms of language found in the world, and the groups of people who speak them.
(The ecology of language. In A. Dil, ed., The Ecology of Language: Essays by Einar Haugen. Stanford, CA: Stanford University Press, 1972)

Voegelin & Voegelin (1964, cited by Haugen, 1972: 328): "in linguistic ecology, one begins not with a particular language but with a particular area"
 

So, let's start with an area: Germanic central Europe.
The ways of speaking "German" is different in these areas:
from the Netherlands to Pomerania
from France to Franconia
And this map shows two famous German isoglosses.
 

The "Rhenish Fan" is a striking cline of variation from standard Dutch to standard German in the area west of the Rhein River.
 

But Linguistic Ecology is more than just "dialectology" or "areal linguistics". We also want to know how these different ways of speaking relate to "other stuff", i.e., even to nonlinguistic facts.
 

Take a look at this map. What might this indicate about the pronunciation of R in northern Europe?
 

A sprachbund, or "linguistic area", or "area of linguistic convergence", or "diffusion area", or "language crossroads" is a group of languages that have common features resulting from geographical proximity and language contact.
 

Scandinavian dialects