Financing for the implementation of the international environmental agreements comes from the treaty parties' own resources. Many new funding mechanisms have been suggested to implement Agenda 21, which at the same time would promote the implementation of multilateral environmental treaties at the national and international levels. The Global Environment Facility (GEF) is the main financial mechanism for projects benefiting the global environment. GEF sponsors programs to help developing countries participate in solving global environmental problems. The debt-for-nature exchanges have been the most commonly used types of trades to date that have provided developing countries with funding for environmental projects and relieved them of part of their debt burden. With the adoption of the Kyoto Protocol, tradable permits are specifically included as an implementation and funding mechanism in an environmental treaty. Environmental taxes are in use in several European countries.