What he associates with Cuba existed before Columbus landed there in 1492, on his journey to the New World. It endured through the Spanish conquest, British colonial rule, several revolutions, and the 1962 Cuban Missile Crisis. What is it? The island nation’s unique plant life, which is the subject of a research project entitled Flora de Cuba.

“Cuba is a true laboratory of evolution,” says Borsch. “More than 50 percent of all plants found on the island – including lichens, ferns, and mosses – are endemic. That means they are found there, and there alone.” Scientific explorer Alexander von Humboldt brought the first dried specimens back to Berlin from the tropical island around 1800. Today, they are kept in the herbarium of the Botanical Museum in Dahlem.

In the 1920s, Ignaz Urban, then vice director of the Berlin Botanic Garden, picked up where Humboldt had left off, embarking on a systematic study of Caribbean flora from Haiti to Cuba and what is now the Dominican Republic. “From then on, there was ongoing cooperation with colleagues in Havana,” Borsch explains. “A third of the flowering plants and ferns of the Caribbean have been described in scientific terms in Berlin since then.”

In the 1960s, the former East Germany and Cuba signed an agreement under which East Germany supplied factory equipment in exchange for nickel, sugar, and tropical fruit from its fellow socialist country. The items from Cuba included the legendary “Cuban orange” – green on the outside, seedy and sour on the inside. Studying the flora of Cuba in monographs was also part of the agreement. From then on, Fidel Castro used funding from East Germany to support the expansion of the botanical garden in Havana, research on plant diversity, nature conservation, agriculture, and forestry.

And while Cuban contract workers and students went to East Germany, botanists from East Germany were welcome in Cuba. “After German reunification, we inherited the treaty, in a way,” Borsch says. The scientific cooperation has been supported since then via Verein der Freunde des Botanischen Gartens in Berlin, a nonprofit organization dedicated to supporting the Berlin Botanic Garden. “Every year, several employees from Cuban institutions spend a couple months each working in our collections. And we send ours there for field trips.”

The Botanical Museum and Botanic Garden in Berlin dedicated a special exhibition titled “Grüne Schatzinseln” (Green Treasure Islands) to this cooperation, which has lasted from Humboldt’s explorations to the present day. The exhibition was shown in Berlin from May 2016 until February 2017. To mark the anniversary of the botanical gardens in Havana, the exhibits were recently shipped to Cuba, where they will remain on permanent exhibition at the Jardín Botánico Nacional de Cuba.

Why are there so many unique plants in Cuba? “It’s partly that Cuba is an island, and partly the particular geological conditions,” Borsch explains. Unusually high levels of heavy metals, especially nickel, are found at points in Cuba’s soil. Many of the local plants are well adapted to these conditions; some even store the metal.

Alongside comprehensive documentation of the island’s plant life – the 22^nd monograph on Flora de la República de Cuba was just published recently – the botanists from Berlin are interested in other aspects, such as the evolution and relationships between the organisms found on the islands of the Caribbean and those of the other countries in Central America, Mexico, and northern South America.

“The plant collections are crucial to this work. That means it is important for the herbaria in Berlin, Havana, and other places around the region to be digitized and well connected,” Borsch emphasizes. It took 40 years of field work to collect sufficient material for comparative analyses of a single group, box trees. The researchers are currently focusing on lichens. They discovered various new species within just a few days on two field trips.

But there is one thing that has Borsch worried: “So far, we’ve only documented a third of Cuba’s flora. If we keep going at this pace, we won’t be done until 2060! And by then, a lot of things may already have been destroyed.” In terms of sustainable development and biodiversity management, the process needs to go faster.

As a result, the researchers working on this “green inventory” plan to prioritize plant families that are of special ecological importance in the future. They include the Rubiaceae, the coffee family, which incidentally also includes the woodruff found in Europe. It is the plant family with the most species in the Caribbean. Borsch also plans to work on the digitization of the collections.

Invasive Species Threaten Native Flora

Unlike in Germany, biodiversity in Cuba is not threatened by the consequences of intensive agriculture. “The areas used to grow tobacco and sugarcane are relatively small, and they were reclaimed back in the colonial era.” But invasive species that displace native flora are increasingly spreading. These include the marabu, a thorny shrub from the Faboideae subfamily, which was introduced from Africa.

Nickel mining and the expected development of tourist infrastructure could also be problematic, depending on what direction they take. Cuba is aware of its green treasures, though, and has set aside large swaths of land as protected natural areas, especially in the south of the island. For example, Alejandro de Humboldt National Park, which stretches over 706 square kilometers and also encompasses mangrove forests and offshore coral reefs, was named a UNESCO World Heritage natural site in 2001.

Little about the documentation of flora has changed since Humboldt’s time, incidentally. While polymath Humboldt drew pictures of the plants, the first step today is to photograph them. The characteristic parts of a species – leaves, for example, or flowers – are then cut off and dried between sheets of newspaper. Delicate parts of flowers are sometimes preserved in alcohol. It is also common practice to collect seeds for living cultures, take a sample for molecular biology tests, and document soil conditions and the other vegetation found at the site.

Not one, but two herbarium specimens are prepared at once – one stays in Cuba, while the other goes to the herbarium in Dahlem. This site, the largest of its kind in Germany, holds four million plants, including about 100,000 from the Caribbean, and another 1,000 to 2,000 are added every year. Stored in darkness at 50 percent humidity and about 18° Celsius, they can survive for centuries. Each and every one serves as documentation of one highly specific plant species.