In African savannahs, or grasslands, wildfires can either be destructive or beneficial. It all depends on when those fires occur. Scientists at the World Agroforestry Center have developed a system to determine the best time to set the savannahs ablaze.
Savannahs stretch across many parts of Africa. But scientists concentrated their research on grassland conditions similar to the Sahel and South Sudan. When wildfires spread uncontrolled, the heat and flames can cause damage on several levels.
“Many components of the ecosystem can be affected. The biodiversity itself, the soil composition and structure and gas emission and greenhouse gas emission into the atmosphere,” said Cheikh Mbow, senior climate change scientist with the World Agroforestry Center in Nairobi, Kenya.
“Fire is seen as one of the biggest drivers of deforestation in some ecosystems. And it contributes widely to the reduction of the ecosystem services, which [are] the basis of most of the livelihoods in Africa in poverty conditions. So we are worrying about fire because of the many impacts and implications for the human beings.”
Fires in savannahs are common.
“If you look at African images from [a] satellite in the dry season, it appears that most of the ecosystem, which has some level of dryness, will have fires on a regular basis. There have been many attempts in the past, since colonial time actually, to, sort of, ban fire in our ecosystem, but they never succeeded. They never succeeded because fire is a tool,” said Mbow.
Fire is used as a tool by local populations, for instance, when they’re gathering honey, clearing land or desiring new vegetation growth. Mbow says nearly all of the fires in the savannahs are caused by humans. Nature plays a very small role.
“The conditions in which natural fire can occur [are] when lightning happens, for instance. In Africa, when lightning happens in these tropical areas that’s a period during which we have rain. It’s wet. When it’s raining, that’s the time we have lightning, and it’s very unlikely that when it’s raining fire can take place,” he said.
With climate change, he said, there’s concern the savannahs will become even more dry, making destructive wildfires much more likely.
That’s why scientists at the World Agroforestry Center and their partners developed a system to pinpoint the best times to intentionally set fires. It’s known as early burning. It consumes layers of biomass before they build-up to highly combustible levels. Efforts to prevent fires altogether can actually make things worse.
“If you protect this area for five years, let’s say, or 10 years, you’ll have a dangerous amount of biomass. Fire not only consumes the biomass, it also destroys all the characteristics of the ecosystem, which makes this ecosystem viable. I’m thinking about microorganisms in the soil, small animals. So it’s a bit dangerous to over protect the ecosystem,” he said.
So an early burn, Mbow said, needs to be done when the conditions are just right – not too wet or not too dry. Fires intentionally set at that time not only consume the biomass, but prevent dangerous fires later in the season.
“There are many factors in determining fires. The one factor is the grass moisture, but also the grass load. The biomass load is extremely important. The second important factor is the atmospheric parameters – air temperature and wind. And the third one is the topography. If you are in heavy conditions, it’s very risky sometimes to use fire. As they go uphill they become stronger and very difficult to control. So there are many, many aspects which should be in consideration. And there is no silver bullet or one-size-fits-all situation.”
The early burns are generally fast moving and stay mainly on the surface. They cause only minor damage to trees, soil nutrients or microorganisms.
The recommendations for controlled fires in African grasslands can be found in the February issue of the Journal for Arid Environments. Mbow said that he hopes African governments will consider implementing them. However, he added, few countries on the continent currently have resources for fire management.
2017届高考英语二轮复习单句语法填空:专题10 定语从句(含解析)
2017届高考英语二轮复习语法综合演练:专题10 定语从句(含解析)
2014届高考英语一轮复习 Unit2《English around the World》词汇与短语全方位训练 新人教版必修1
2014届高考英语一轮复习 Unit5《Nelson Mandela a modern hero》单项填空全方位训练7 新人教版必修1
2017届高考英语二轮复习单句语法填空:专题13 特殊句式(含解析)
50周年叫金婚,那7年、9年叫什么??
2017届高考英语二轮复习语法综合演练:专题6 动词短语(含解析)
2014届高考英语一轮复习 Unit5《Nelson Mandela a modern hero》单词拼写全方位训练 新人教版必修1
2017届高考英语二轮复习语法综合演练:专题4 形容词、副词(含解析)
2014届高考英语一轮复习 Unit4《Earthquakes》阅读理解全方位训练3 新人教版必修1
2014届高考英语一轮复习 Unit5《Nelson Mandela a modern hero》单项填空全方位训练6 新人教版必修1
2017届高考英语二轮复习语法综合演练:专题11 名词性从句(含解析)
2017届高考英语二轮复习单句语法填空:专题5 介词与介词短语(含解析)
2017届高考英语二轮复习单句语法填空:专题7 动词的时态和语态(含解析)
2014届高考英语一轮复习 Unit5《Nelson Mandela a modern hero》短文改错全方位训练1 新人教版必修1
2017届高考英语二轮复习语法综合演练:专题8 情态动词与虚拟语气(含解析)
2017届高考英语二轮复习单句语法填空:专题4 形容词、副词(含解析)
2014届高考英语一轮复习 Unit4《Earthquakes》阅读表达全方位训练1 新人教版必修1
2017届高考英语二轮复习单句语法填空:专题3 代词(含解析)
2017届高考英语二轮复习单句语法填空:专题11 名词性从句(含解析)
美文赏析:我决定从此过上幸福的生活
2017届高考英语二轮复习语法综合演练:专题2 冠词(含解析)
2017届高考英语二轮复习单句语法填空:专题8 情态动词与虚拟语气(含解析)
2014届高考英语一轮复习 Unit4《Earthquakes》任务型阅读全方位训练1 新人教版必修1
2017届高考英语二轮复习语法综合演练:专题12 状语从句与连词(含解析)
2017届高考英语二轮复习语法综合演练:专题9 非谓语动词(含解析)
2014届高考英语一轮复习 Unit1《Friendship》阅读理解全方位训练4 新人教版必修1
2017届高考英语二轮复习单句语法填空:专题9 非谓语动词(含解析)
2014届高考英语一轮复习 Unit4《Earthquakes》阅读理解全方位训练2 新人教版必修1
2017届高考英语二轮复习单句语法填空:专题12 状语从句与连词(含解析)
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |