to stimulate economic growth, while US dollars were also made legal tender. Certain restrictions on emigration were eased, allowing more discontented Cuban citizens to move to the United States. Further democratization was to be brought in by having the National Assembly's members elected directly by the people, rather than through municipal and provincial assemblies. Castro welcomed debate between proponents and opponents of the economics reforms—although over time he began to increasingly sympathise with the opponent's positions, arguing that such reforms must be delayed. Castro's government diversified its economy into biotechnology and tourism, the latter outstripping Cuba's sugar industry as its primary source of revenue in 1995. The arrival of thousands of Mexican and Spanish tourists led to increasing numbers of Cubans turning to prostitution; officially illegal, Castro refrained from cracking down on prostitution in Cuba, fearing a political backlash. Economic hardship led many Cubans toward religion, both in the form of Roman Catholicism and Santería. Although long thinking religious belief to be backward, Castro softened his approach to religious institutions and religious people were permitted for the first time to join the Communist Party. Although he viewed the Roman Catholic Church as a reactionary, pro-capitalist institution, Castro organized a visit to Cuba by Pope John Paul II for January 1998; it strengthened the position of both the Cuban Church and Castro's government. In the early 1990s Castro embraced environmentalism, campaigning against global warming and the waste of natural resources, and accusing the US of being the world's primary polluter. In 1994 a ministry dedicated to the environment was established, and new laws established in 1997 that promoted awareness of environmental issues throughout Cuba and stressed the sustainable use of natural resources. By 2006, Cuba was the world's only nation which met the United Nations Development Programme's definition of sustainable development, with an ecological footprint of less than 1.8 hectares per capita and a Human Development Index of over 0.8. Castro also became a proponent of the anti-globalization movement, criticizing US global hegemony and the control exerted by multinationals. Castro maintained his strong stance against apartheid, and at the 26 July celebrations in 1991, he was joined onstage by Nelson Mandela, recently released from prison. Mandela praised Cuba's involvement in battling South Africa during the Angolan Civil War and thanked Castro personally. Castro later attended Mandela's inauguration as President of South Africa in 1994. In 2001, Castro attended the Conference Against