"Illegal trade in diamonds and precious stones, rare metals or those of great strategic value, wood, biological material and animal products, such as ivory trafficking and the related killing of elephants, fuels political instability, organised crime and terrorism," he said in a speech in the Kenyan capital, Nairobi.
"We cannot be silent about forms of illegal trafficking which arise in situations of poverty," he said, just two weeks before Nairobi hosts a key ministerial meeting of the World Trade Organisation.
Figures published earlier this year by Amnesty International say conflict diamonds, which account for four percent of total global production, have helped finance civil wars and prop up military dictatorships.
The pope's remarks on wildlife trafficking were likely to hit home in Kenya, where ivory smuggling is rampant and which is currently trying to stamp out poaching to protect its remaining elephant population.
The Argentine pope also warned against "the globalisation of indifference" and the danger of becoming resigned to "new forms of slavery, human trafficking, forced labour, prostitution and trafficking in organs.