The solar-powered listening posts detect illegal loggers and poachers in remote areas.
Using audio recognition software, old solar-powered phones can pick up sounds from chainsaws.
The event challenges participants to build platforms around power, deforestation and greenhouse gas reduction.
Greenpeace's campaign to have toy company Mattel switch its paper sourcing policy has worked.
Rising temperatures and deforestation threatens the sensitive cocoa plant, the source of chocolate.
A bio-engineered brick could replace traditional kiln-fired bricks.