Image caption Historically, fire has played an important role in shaping landscapes' flora and fauna

A model has helped shed light on how human-started fires shaped Africa's landscape, researchers report.

Before human activity became widespread, most fires were caused by lightning strikes during the continent's wet seasons, they said.

As the human population expanded, more fires occurred during the dry season, triggering a shift in the impact of fires on Africa's ecology, they added.

The findings appear in the Proceedings of the National Academy of Sciences.

"People have always been aware that there have been a lot of wildfires in Africa," said co-author Sally Archibald, senior researcher at the Council for Scientific and Industrial Research, South Africa.

"When we started getting satellite data, it became even more apparent that there is a lot of burning that happens.

"This made people concerned; they were worried that there was too much fire in Africa."

Human impact

Dr Archibald explained that the team decided to develop the model in order to understand current conditions, and whether there was now too much burning compared with the time when humans were not so prevalent and influencing landscapes' "fire regimes".

It has been estimated that early humans could have had the ability to start fires about 300,000 years ago, but the real impact was from about 70,000 years ago as human populations became more widespread.

"We really cannot make good (conservation) decisions unless we can understand how humans have manipulated fire," added Dr Archibald.

"It is really interesting that we are the only organism in the world to have harnessed fire, and we need to understand how that may have changed the systems in which we live."

The theoretical model, which focuses on Africa's grassland habitats, took data on how people have used fire and linked it to archaeological knowledge of how human populations in the region evolved.

Dr Archibald told BBC News that one of the paper's key insights was that, according to the model, wildfires were currently at their "lowest level for the past 40,000 years or so".

"There is less wildfire in Africa now, even though it looks like there is such a lot when you look at the satellite data, because of the way that people have been using the landscape."

She explained that the model could be used to help national parks develop fire management policies.

"They are trying to develop fire management policies and they want to burn their landscapes in a way that will maintain biodiversity," she said.

"That becomes quite a tricky question in Africa because you cannot just say 'well, I will not light fires at all, only natural fires will be allowed'.

"People have been in Africa for over a million years, so you cannot try to suppress all human fires. You have to include humans as part of your system, and fire managers still need some guidance on what is the best way to burn these systems and yet maintain biodiversity."