By the early 1980s, Costa Rica had devastated its natural rainforest with an incredible rate of ongoing deforestation. But by the end of the decade, it had cut the deforestation rate by more than half, and would drop it a whopping 80% in the next five years.
What political/economic and cultural changes made this possible?
I cannot speak for the whole country, but I know a lot about what happened around the town of Monteverde in Guanacaste. Costa Rica benefitted from the ecotourism boom that began in the 80's and continues right through to today. They were well positioned.
It started with their decision to demilitarize after WWII. This allowed them to invest in health care and education. They were able to do this because of their close relationship with the US. You can read about that here. https://en.wikipedia.org/wiki/Costa_Rica%E2%80%93United_States_relations
In 1950, a group of American Quakers moved to Costa Rica due to their opposition to war. They went there to be farmers. They started an English speaking school in what is now Monteverde. They started a dairy that made American style cheese and ice cream.
The US sent thousands of Peace Corps volunteers to Costa Rica. Many of them returned for holidays, some stayed. Some came back to retire. Costa Ricans learned to speak English.
By the 60's, American biologists came to study the biodiversity. Costa Rica sits in the middle of the Central American Biodiversity hotspot. They had ties to the Quakers who lived there. American backpackers started to arrive. Hostels began to appear, started by the Quakers.
First it was the golden toad that became famous (it is now extinct) then the quetzal. The American scientists convinced the Quakers to preserve some of the land that they had purchased. They only used the upper section of their communal lands for hunting. They wanted it preserved for its use as a water reservoir. This became the Cloud Forest Reserve. Almost all tourists to CR came here.
At this point, the late 60's to early 70's, most of CR was still impoverished. Monteverde was doing very well. I don't know if other places in CR also benefitted from tourism at this point.
In the early 80's, the first zipline in the world was started in Monteverde. Then in 1987, thousands of school kids raised funds to create the Children's Eternal Rainforest after one school in Sweden heard from a US biologist about the loss of habitat for tropical creatures there. Soon, 44 countries were involved.
So, a lot of it has to do with the fact that they have an incredible country to begin with, but that they were well-positioned to take advantage of ecotourism and the expat economy because of a long standing relationship with the US.
Okay, so there is a long set-up, and CR was "well-positioned" as /u/english_major explains very well! But what compelled government, business, policy action in the mid/late 1980s to reverse a situation that had been continuing even in the face of developing popular enthusiasm? Did the tourism industry suddenly provide a higher proportion of the CR's economy, and the government took notice? Did the government specifically support the tourism industry having made up its mind for other reasons? Were specific leaders involved?
Costa Rican deforestation was largely a result of a continuation of colonial ideals. Even though costa rica has been independent for a fairly long time, it still was heavily tied up with European industrial activities. Costa Rican environmentalism resulted from several political and economic changes in the region including increased respect for indigenous groups, government subsidies for environmental services, and the growing market for ecotourism in the world. Many of Costa Rica's environmental initiatives were aided by their proximity to the United States who became increasingly involved in foreign environmental issues in the 1980s. Some information on those activities can be found [here] (http://costarica.usembassy.gov/environment.html). Most of the environmental action was started due to global demand for environmentalism that Costa Rica wanted to cash into in order to reduce poverty. for more information on the history of Costa Rican environmental movements, I suggest The Green Republic: A Conservation History of Costa Rica, by Sterling Evans (1999)
The OP asked for specific drivers of anti-deforestation policy in the late 80s / early 90s, so here's a big one: the publication of Gary Stiles and Alexander Skutch's "A Guide to the Birds of Costa Rica" in 1989. ( http://www.amazon.com/Guide-Birds-Costa-Rica-Civilization/dp/0801496004 ) It was the first detailed guide to birdwatching in Costa Rica, and went into great detail about the country's unique ecosystem as well as its position as a "bottleneck" for migratory birds. Skutch had been writing about birds from Costa Rica for years, but this "definitive" guide immediately spurred a wave of international bird watcher travel to Costa Rica.
These new tourists - unlike the surfers and backpackers that came before them - were extremely wealthy, well-connected, and interested in one thing: unspoiled forest habitat. The quetzal in particular was both highly prized by birders and deeply threatened by deforestation. It was easier for policy makers and environmentalists to draw a direct line from these very specific tourists to this very specific threat, rather than fuzzier ideas about "eco-tourism", so keeping forests intact for birds became a top priority. Carrara National Park is a good example - it was a semi-protected reserve that became a national park shortly after "Guide to Birds" was published - not a particularly beautiful or walkable forest, but quite valuable as quetzal macaw habitat.