LONDON (Reuters) -Billions of dollars of debt deals aimed at protecting vital ecosystems from Africa to Latin America are at risk of unravelling or may need rework amid concerns that crucial U.S. backing is about to dry up under President Donald Trump. The 'debt-for-nature' swaps, which reduce a country's debt in return for conservation commitments, have gained traction in recent years with deals involving the Galapagos Islands, coral reefs and the Amazon rainforest among the most prominent. The U.S. International Development Finance Corporation (DFC) has been a key player, providing political risk insurance for over half of the deals done over the last five years, accounting for nearly 90% of $6 billion of swapped debt.