Education and early career
Co's education in Botany did not follow the usual track. He did not finish his bachelor's degree until 2008 because he was always too busy doing research out in the field. Dr Perry Ong, director of the Institute of Biology at the University of the Philippines Diliman summed it up at Co's wake by saying “Leonard Co entered UP as botany freshman in the early 70s and never left.”
In 2008, with Co already informally considered one of the foremost experts in his field, University of the Philippines Diliman named him the last graduate of the Bachelor of Science degree in Botany; some time in the decades since Co's enrollment, the course had been merged with the bachelor's degree in Zoology to form the bachelor's degree in Biology program. This unorthodox academic path also earned Co another distinction in the annals of UP: Co submitted his book on the medicinal plants of the Cordilleras in lieu of a thesis, making him the only student to graduate from the BS Botany degree without submitting a thesis.
Co worked as a museum researcher at the University of the Philippines Institute of Biology, and as a senior botanist at the Conservation International-Philippines.
Co was the founding president of the Philippine Native Plants Conservation Society. and received credit for discovering eight new species of plants. Aside from these, two species of Philippine endemic plants have been named in his honor: the Mycaranthes leonardi orchid and the Rafflesia leonardi, a parasitic plant species of the genus Rafflesia endemic to the Philippines and known for bearing the third largest flower in the world.
A year before his death, Co also documented the flora of the Bataan National Park, coming up with a catalog that lists 160 unique plant species, essential for guiding reforestation efforts on the 23,668-hectare park centered around Mount Natib.
- Philippine Botanical Treasures and the Legacy of Leonardo L. Co: November 19 and 20, 2011, Tambunting Hall, National Museum of the Philippines
Death and legacy
Co, forester Sofronio Cortez and farmer Julius Borromeo, were working on a biodiversity project under the auspices of the Energy Development Corporation when they were killed in an incident involving members of the 19th Infantry Battalion of the Armed Forces of the Philippines in the forests of Kananga, Southern Leyte on November 15, 2010.
The members of the army unit claimed that Co's group had been caught in the crossfire in a fight between their unit and the New People's Army, but this claim was challenged by numerous investigating groups, including the Philippine National Police and the Philippines' Commission on Human Rights. The Philippines' Department of Justice eventually filed charges against the soldiers involved, and the case is currently in the courts.
During his wake, Co was conferred the rare honor of having his coffin briefly displayed in front of the University of the Philippines Diliman's copy of the UP Oblation - the iconic symbol of the University of the Philippines.
In accordance to his wishes, a third of his ashes was scattered in the 16-hectare forest dynamics plot he built and worked on in Palanan, Isabela, up in the Sierra Madre Mountains. Another third was given to the UP Institute of Biology and scattered under one of UP's trees, to symbolize that Co would always be a part of the university. The last third of his ashes was given to his family.
On May 2, 2011, Co was posthumously conferred the National Academy of Science and Technology – Hugh Greenwood Environmental Award for his contribution in profiling forest biodiversity. 
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