Page 95 - University of Pretoria Research Review 2017

Foreword
Introductory Messages
DEVELOPMENT AND CHANGE
PEOPLE AND CONTEXTS
FABI, forests and fungi
The status of coastal forests
Pieter Olivier, Conservation Ecology Research Unit (CERU), Department of Zoology and Entomology
HEALTH AND WELL-BEING
PLANET AND SUSTAINABILITY
Awards
Lead Researchers
93
Fragmentation of the world’s forests is affecting biodiversity directly through the loss of core forest habitat, and indirectly by creating forest edge areas. It is estimated that approximately half of the world’s forests are now situated within 500 metres of a forest edge.
Dr Pieter Olivier’s work on coastal forests in South Africa during his doctoral and postdoctoral studies
in the Conservation Ecology Research Unit (CERU), Department of Zoology and Entomology, contributed to an international study that considered the global impact of forest edges on forest vertebrates. Led by
Dr Marion Pfeifer, Newcastle University, and Dr Robert Ewers, Imperial College London, the study assessed the impact of human-induced forest fragmentation on the abundance of 1 673 species of mammals, birds, reptiles and amphibians around the globe.
The study, published in 2017 in the journal Nature*, found that 85% of all vertebrate species are affected by forest edges globally. As a result, the community of animals that persists near edges bears little resemblance to that found in the forest core. Half of the world’s forests now house disrupted vertebrate populations. In particular, the researchers found that 11%, 30%, 41% and 57% of bird, reptilian, amphibian and mammalian species, respectively, show strong declines in abundance towards forest edges.
The researchers used a new method that accounts
for the continuous changes in habitat quality across fragmented landscapes, making their analysis markedly different from previous global analyses of biodiversity responses to land-use changes, which typically do not incorporate gradations of change.
Dr Olivier’s earlier work on coastal forests in South Africa, supervised by Professor Rudi van Aarde, Director of CERU, was based on modelling estimates of forest loss. Their results show that as much as 82% of coastal forests in this country have been lost over the past two centuries. Forest fragments are now also smaller, fewer, further apart and more ‘hemmed in’ by
human-land use than in the past. This extent of forest loss means that forests are now likely to harbour an ‘extinction debt’; this means future biodiversity losses that current or past habitat destruction will incur, but which have yet to be realised, because of the time delays in extinction.
Working on bird species, researchers at CERU found that insectivorous bird species are the group most likely to be negatively affected by forest fragmentation. Their research further suggests that extinctions may be prevented by conserving natural or restoring anthropogenic matrices (that is, habitats that surround forest fragments), as well as by increasing forest
areas. When matrix habitats are natural (for example, grasslands and woodlands) small and large forest fragments harbour similar numbers of bird species. However, when the matrix is compromised by human land use (for example, sugarcane and Eucalyptus plantations), small forest fragments have far fewer species than larger fragments. Matrix transformation may therefore cause local extinctions in smaller forest fragments.
Survey team: Pieter Olivier (UP), Marion Pfeifer (University of Newcastle), Thabani Mthethwa (field assistant), and Marc Freeman (MSc student, UP).
* M Pfeifer et al. Creation of forest edges has a global impact on forest vertebrates. Nature, 551, 187–191 (09 November 2017).