List two ways how humans impacted the geography of Panama by constructing the Panama Canal.

Considered one of the wonders of the modern world, the Panama Canal opened for business 100 years ago this Friday, linking the Atlantic and Pacific Oceans and providing a new route for international trade and military transport.

At the time it was built, the canal was an engineering marvel, relying on a series of locks that lift ships - and their thousands of pounds of cargo - above mountains.

But thousands of workers died during its construction, and its history has seen no shortage of controversy, including a contentious transference of authority from the US to Panama in the 1970s.

Work recently began on a substantial expansion effort that will allow the canal to accommodate modern cargo needs.