pastures for cattle raising, at an ever-faster rate during the last 500 years. In 1985, realizing that widespread development in northwestern Costa Rica was rapidly decimating the forest in which they conducted their research, Janzen and Hallwachs expanded the focus of their work. Janzen and his wife helped to establish the Area de Conservación Guanacaste World Heritage Site (ACG), one of the oldest, largest and most successful habitat restoration projects in the world. They began with the Parque Nacional Santa Rosa, which included of pasture and relictual neotropical dry forest and of marine habitat. This eventually became the Área de Conservación Guanacaste, located just south of the Costa Rica-Nicaragua border, between the Pacific Ocean and the Cordillera de Tilaran which integrated four different national parks. Together these house at least 15 different biotopes, viz (mangroves, dry forest and shrubs, ephemeral, rainy season, and permanent streams, fresh water and littoral swamps, evergreen rain- and cloud forests...) and ca. 4% from world's plant, mammals, birds, reptiles, amphibians, fishes and insects diversity, all within an area less than . It is one of the oldest, largest and most successful habitat restoration projects in the world. As of 2019, it consists of . The park exemplifies their beliefs about how a park should be run. It is known as a center of biological research, forest restoration and community outreach. Habitat restoration is not a simple matter. Not only must one fight against hundreds of years of ecological degradation, manifested in the form of altered drainage patterns, hard to eradicate pastures, compacted soils, exhausted seed banks, diminished adult and propagule stocks, proliferation of fire-resistant and unpalatable weeds from the old world tropics and sub-tropics. Also one is faced with the difficulties of changing a culture which coevolved with, profited from and can become miserable with such a system. For this reason ACG was conceived as a cultural restoration project, which, to paraphrase its natural counterpart, ought to be grown as well. ACG integrates complementary processes of experimentation, habitat restoration and cultural development. The techniques used include: Active restoration, artificial dispersal of propagules from plant species native to the Guanacaste habitats Passive restoration by means of fire, anti-poaching and herbivore control Ecological education and sensibilisation Personal life Janzen is married to ecologist Winifred Hallwachs, who is also his frequent research partner. Of Hallwachs, Janzen has said, "We did these things together," and "we are very much