Dry leaves crunch underfoot as we enter Kaya Muhaka, a sacred forest of the Mijikenda a few kilometres inland off Kenya’s South Coast. It is cool and quiet inside the sacred grove.
Kaya Muhaka is home to some rare tree species. One is the gigasiphon macrosiphon, known as mnyanza in the local Digo language, which Dr Itambo Malombe of the East African Herbarium at the National Museums of Kenya discovered while conducting an evaluation of plant and insect biodiversity for the National Council for Science and Technology in the Kaya forests between 2008 and 2010. Dr Malombe’s team found fewer than 10 trees in the 350-acre Kaya.
Gigasiphon macrosiphon derives its name from the Latin words giga and macro, which mean large, probably referring to the large fruits and flowers of the tree. Siphon means tube — the more than 15cm long tube that attaches the flower to the plant.
The first scientific description of the tree was in 1915. It was feared extinct in Kenya until 1990, when Quentin Luke and Ann Robertson rediscovered some in Kaya Muhaka and the nearby Gongoni forest.
But it was not the first time the tree was found in Muhaka. Records seen by Antony Githitho and Mr Luke of National Museums of Kenya showed that a flowering gigasiphon was found in Muhaka in December 1918 — apparently a new flowering record, as it is known to flower between May and August — by F.L. Kelly, an assistant conservator of forests in Mombasa at the time.
Another record was by Bernard Verdcourt in 1957 at Mrima Hill. Dr Malombe found the species in Mrima Hill forest in 2010. There were only three mature trees.
Mrima Hill has been in the news recently after the discovery of large rare earth deposits. Quentin Luke has been studying coastal flora for years, and has found several species new to science, with many named after him.
Elsewhere in East Africa, the gigasiphon macrosiphon is found on Tanzania’s Rondo Plateau, where Luke and Henry Ndangalasi of the University of Dar es Saalam found three mature trees.
At the sixth East African Plant Red Listing Authority meeting in April 2012 at the International Union for Conservation of Nature headquarters in Nairobi, Dr Malombe reported the existence of the tree in Muhaka, Gongoni and Mrima forests.
Both Kenya and Tanzania were reported to have 33 trees. The meeting then declared the gigasiphon macrosiphon critically endangered under IUCN’s Red List and placed it among the first 100 priority species for conservation in the world.
“A plant is listed as CE when there are fewer than 50 mature individuals in the wild, coupled with observed population stagnation such as lack of young trees and/or no successors as well as recorded habitat degradation,” Dr Malombe said.
Funded by the Mohamed Bin Zayed Conservation Fund to monitor and map the trees, by June 2013, Dr Malombe’s team had located 208 mature trees and provided GPS co-ordinates, which will be made available on a website. With the new data, the tree will revert to the endangered category.
Our guide, Said Ali Chidzinga, a field assistant, led us to one of the trees, a towering hulk 12 metres tall, with a 15-metre diameter canopy. Only two enormous creamy white flowers hung on the tree. Higher up, an Angolan colobus monkey feasted on the flowers. Dr Malombe pointed to the saplings and the walnut-size seeds on the ground. The saplings are dying and nobody knows why.
Ten kilometres from Kaya Muhaka is Kaya Gongoni, which is 10 times bigger, with a swamp at its edge. A new road cuts through the forest, with water pipelines and electricity poles lining it.
Gongoni has several gigasiphon macrosiphon trees.
“Each kaya is different, with the species varying within small distances,” Dr Malombe said. “For the first time, we’re observing the dying of a single species that we know so little about. We need to investigate why seeds are germinating but not growing to maturity.”
The insect that pollinates it remains a mystery.
Dr Esther Kioko, an entomologist from NMK, was in the entourage to begin the investigation. The hawksmoth seems to be a likely candidate, as the nectar sac nestles deep within the narrow stigma of the flower.
“There is potential for the gigasiphon to be planted as an ornamental tree in botanic gardens, which will ensure its survival and store the seeds in a genebank,” Dr Malombe said.
Threats to the tree include roads cutting through the kaya and farming on the edges of the forest, which may lead to encroachment and destruction of the trees.
“We need surveys, regular monitoring and to create conservation awareness about G.macrosiphon and find out what more is in the kayas. And we need more government assistance,” he said.