EPOW - Ecology Picture of the Week

This Is How We Fill the Valleys

Vorë, Albania

Explanation:  Look closely at the patterns of human settlements in these aerial photos I took  during a passage over central Albania just off the Adriatic Sea.  
  

What do you notice first?  It is that the valleys are fully occupied and developed.  

So it has been for centuries, here and elsewhere around the globe.  Why?  

It is because valleys are far easier to access than are the steep surrounding mountains.  Valleys have rivers which serve as transportation corridors for people and goods.  Valleys have colluvial soils that can be fertile for agriculture.  Valleys may already have attracted wild plants and animals that can serve as subsistence foods.  Valleys have sediments that can hold substantial groundwater for wells and irrigation.  Valleys provide room for growth.  These and other reasons explain humanity's biogeographic, socioecological, and sociobiological attraction to valleys.  

In general, valleys provide the best habitats for humans to settle, prosper, and spread.

Can you think of some parallels to this in the natural world?  

One instance involves the spread of Barred Owls (Strix varia) down the western edge of North America.  Barred Owls often first invade hardwood forests in bottomlands and valleys, and then move upslope to intersect with, and outcompete, threatened Northern Spotted Owls (Strix occidentalis caurina).  The Barred Owl's habitat preference is not unlike our own.  
  

The town of Gjokaj in west-central Albania continues this pattern
of valley occupancy, here strikingly shown as linear features
along a riverine causeway.