Carefully managed fires can enhance biodiversity in Africa’s fragile savannas

Researchers at Britain's University of York found that using highly diverse fire types increases the diversity of mammals and birds in wet savannas, including the Speke's weaver, a range-restricted species. Credit: Colin Beale, University of York.
17 March 2018

BONN, Germany (Landscape News) — The burning of biomass, including wood and organic matter, has played a critical role in the management of Africa’s savannas for millennia, helping control undesirable plant species, facilitating access to new growth forage, and eradicating pests and parasites.

It has also been used to manipulate habitats – although its effects on biodiversity have been found to be both positive and negative.

Now, new research conducted by a team of researchers from Britain, South Africa and the United States goes beyond a homogeneous perception of fires to acknowledge “pyrodiversity,” showing how distinct types of fire can provide a wider range of habitats where species can live and reproduce successfully.

“Fire is often viewed as homogeneous, but in reality there is a range of different fires characterised by variation in size, intensity, season and frequency of burning,” said lead author,  Colin Beale, from the University of York in an interview with Landscapes News. “We found that in wet savannas, increasing the range of different types of fire in an area allows a wider number of species to thrive.”

The first continent-wide analysis of burning regimes in protected savanna areas – demonstrates consistent and positive consequences for multiple species, allowing scientists to glean insights into how fire can be used as an effective tool.

In a departure from previous studies, which have tended to be small-scale and applied across a limited range of environmental conditions and species, the researchers analyzed fire data from satellites and distribution maps of bird and mammal species over a 15-year period.

Effects on the savanna, characterized by grasslands, shrubs and trees, varied depending on environmental conditions and fire characteristics. In wetter areas – where annual rainfall exceeds 650 mm year – pyrodiversity increased species richness by 27 percent for mammals and 40 percent for birds, including rare species such as the Rufous-tailed Weaver and the Black-bellied Sunbird.

Researchers found that larger fires reduced biodiversity richness but variability in fire season could increase the diversity of both woody plant and grass structures.

Similar effects were not observed in dry savannas – areas receiving annual rainfall below 650 mm year – which researchers attributed to the relative scarcity of woody plant material. “It is in intermediate areas where trees and grasses can both grow freely that processes like fire can have the most impact on controlling the habitat structure,” said Beale.

The analysis provides a better understanding of when, where and how often vegetation should be burned. Strategies also need to be tailored to the requirements of specific goals. Maximizing tick control, for example, means burning vegetation when young ticks are searching for animals and cannot hide in soil fast enough to escape flames.

On the other hand, removing long grass to enhance visibility and restrict the number of hiding places for poachers requires a burning strategy that is initiated at the start of the dry season.

A “toolkit” is now being developed to support conservation managers so they can use fires more effectively. It will help them to articulate their objectives when burning; determine what the impacts of their current fire regimes are; and identify how and where improvements can be made.

“Our hope is that we can help people realise how subtle a tool fire really is and that its use needs a clearly articulated goal before determining how to proceed,” Beale said. “Ideally people will also monitor results on the ground, and if needed, adjust as required.”

It is also important to ensure that national policies, local policies and practices are all aligned so that savannas can be managed to maintain pastoralist lifestyles, he added.

Although savanna grasses are annual and are essentially carbon neutral – they capture carbon dioxide when they grow each year and release the same amount when they are burned – there are some concerns about smouldering wood which can result in the release of strong greenhouse gases such as methane.

Efforts to reduce smouldering and increase the number of animals that can enhance carbon sequestration into soil are management options now under discussion – although no consensus has yet emerged.

Concerns about greenhouse gas emissions should not be allowed to override carefully managed burning strategies, however – given that they can potentially benefit rural communities and protect their livelihoods.

“While the value of burning in certain habitats is unclear and debated, in savannas, the necessity of burning is widely appreciated and people are keen to know how best to use this tool,” Beale said.