Scientists are investigating the "sky island" of Mabu, the BBC reports.
A team of scientists have visited the forest alongside BBC environment correspondent Jonah Fisher. It marks the first time a team of scientists have based themselves right in the centre of the forest.
Research scientist and beetle expert Dr Gimo Daniel is among the team who discovered dozens of new species in what is the largest rainforest in southern Africa.
Dr Daniel had discovered what he believes are 15 new species of dung beetles.
Erica Tovela, a freshwater fish expert from Mozambique’s Natural History Museum, also discovered something new. In the stream that runs through camp, she found a type of small catfish.
Large mammals such as lions, rhinos and buffalos once inhabited Mabu, but they have since been hunted to extinction there, most likely for food during the war.
Deforestation has also had an effect on the population of these mammals, though not as badly as other forests in southern Africa.
Mabu was 'discovered' for the outside world by Professor Julian Bayliss, an explorer and ecologist, in 2004.
Prof Bayliss came across Mabu when he was surveying satellite images of northern Mozambique and found a previously unknown dark-green patch.
At 75 square kilometres, Mabu is the largest single block of rainforest in southern Africa.
It is a medium-altitude rainforest, and protrudes above Mozambique’s lowlands, making it a sky island.
What is a sky island?
Sky islands are isolated mountain ranges surrounded by radically different lowland environments.
The term originally referred to those found on the Mexican plateau and the definition has now been extended to similarly isolated high-elevation forests.
Some sky islands serve as refugia for boreal species stranded by warming climates since the last glacial period.
Herpetologist (snake expert) Edward H Taylor first presented the concept of "islands" on the Mexican plateau in 1940.
The concept was later applied when Natt N Dodge referred to the Chiricahua mountains in south-eastern Arizona as a "mountain island in a desert sea".
The term was popularised by nature writer Weldon Heald, in his 1967 book, Sky Island.
