“There are many ecosystems around the world, that are what we call, dependent on fires. So, the way in which that biome or landscape has formed, historically, over millions of years, has been shaped by fire," said Tercia Strydom, a senior manager at Scientific Services here in Kruger National Park. The majority of her research focuses on soil hydrology and the landscape effects of fire.
“If we weren’t to have fires, maybe a savanna would turn into a very wooded, forested area. If we were to have too many fires, maybe it would become a lot more grass dominated — or barren," said Strydom. "So having the right fire regime for certain landscapes is important.”
That makes sense because fires really do shape the savanna. Fires can change the way in which vegetation grows, along with its structure, composition, and biodiversity.
They can shift animal communities, alter soil chemistry and hydrology, and much more. Such impacts can be seen as direct or indirect results of fire, but it turns out the whole process is a bit more complicated than that.
“It's both how fires affect other parts of the environment, but also how your environment can affect fires,” said Strydom.
For example, grassy areas without many trees are more prone to fire than wooded areas, but such grasslands might not even exist without fire in the first place.
“Once a fire changes the vegetation landscape, that can have an impact on how other animals use the landscape,” said Strydom.
Herbivores will often congregate in recently burned areas. For some, it’s simply a matter of food as grasses regrow while others use such open spaces to keep an eye out for predators.
“So, they tend to sleep in these recently burnt areas because they feel safer," said Strydom. "But on the other hand, we have seen them licking the soil surface, and this is before grasses re-sprouted and grown back.”
That could be for salts and other minerals or even to simply ingest the charred sugars left behind after a burn. Suffice to say though, fires are an essential part of the savanna and many other environments. But such intricate feedback loops can pose significant challenges for managers.
“There are many landscapes around the world in which fires have been outlawed and banned," said Strydom. "And what often happens is that, because fires have always been part of the system, if we try to keep fires out of that system, we get to a point where it is close to impossible."
Kruger actually began as one such landscape. About 80 years ago fires used to be only suppressed, but 70 years’ ago things began to change. Since then, the park has developed an intricate strategy for dealing with fires whilst ensuring that fires maintained its ecological role in these savannas.
“In Kruger, there's certain parts of the park where we want to burn frequent and hot fires for certain ecological reasons. There are some parts of the park where we burn low intensity, less frequent fires," said Strydom. "And then in some parts of the park where we do not put in prescribed fires, we will only burn what we call fire breaks, so safety fires around infrastructure, etc, and but if there's a lightning fire, we will allow a lightning fire to burn to its fullest extent, self-extinguish, as long as there's no threat to property and lives.”
Overall, it’s an intense process that involves looking at biomass accumulation, precipitation, time since last burn, satellite imagery, maps of current and past fires, ground reports from section rangers and of course, post fire monitoring.
In the end, when and where to burn is a carefully calculated decision. Though it is true that the immediate aftermath can at first seem quite desolate. And as we finished our interview, Strydom and I walked to one such place.
“As you can see, we've just approached the recently burnt area that burned a couple of months ago during the dry season. You can see the fire burned through this landscape, but the grass tufts are all still intact," she said. "And you can see now that after the rains have fallen and it's now the next growing season, you can see this new, fresh, very clean, soft leaves that have re sprouted from this tuft.”
And such fresh leaves are more palatable to grazers such as white rhinos and impala who may visit this area shortly after burning. And so, the loop continues.
