Technique developed in Kenya offers a refined way to map tree cover



File 20170908 25859 9cthdc.jpg?ixlib=rb 1.1
Each year satellite images and maps show patterns linked to land use/cover change.
Flickr/NASA

Michael Marshall, World Agroforestry Centre (ICRAF)

Scientists at the World Agroforestry Centre in Nairobi, Kenya, recently pioneered a new approach which uses satellite images and maps to show patterns linked to land use and cover change on a yearly basis. Though the technique was developed in Kenya, it can be used regionally and potentially across the world.

“Land use and cover change” are terms used by scientists to define changes to the earth’s surface. This can be due to natural causes or because of the way in which land is put to use by people. Land use refers to what’s being done on it, for example mechanised farming, while land cover refers to what is physically on the land, for example what crops are being grown.

What’s important about the new approach is that the maps consist of an array of both physical and human geographic data to explain changes. It can also be used in combination with large-scale climate models, for example to understand how changes in vegetation in East Africa might be affecting climate in other regions of Africa.

In Kenya’s case, the system mapped changes in agriculture and natural vegetation with information from over a 30-year period. Using a series of aerial photographic surveys – which could be used to distinguish specific crops or natural vegetation – and freely-available spatial data such as rainfall, and population density, interpreters were able to classify Kenya’s land use and cover change. They were then able to construct maps of this change on a yearly basis without extensive and costly field visits typically used when mapping change.

Understanding land use and cover change is important because they both affect how land responds to the environment. Many of the changes are human-induced – for example the way that people use the land can lead to habitat loss, increase the stress of life that the land supports, affect greenhouse gas emissions and storage, modify runoff and ground water storage, or alter the climate.

Deforestation, perhaps the most well-known type of land use and cover change, comes about primarily from agriculture and logging. It has an impact on the world’s climate because trees store huge amounts of carbon that would otherwise be in the air trapping heat. The absence of trees therefore contributes to global warming.

Deforestation also affects people locally, particularly in the global south. Forests help regulate rainfall and water storage, and the help maintain a high level of biodiversity.

Much of the global north has seen an increase in tree cover in recent years. But much of the global south continues to show declines due to population growth, weak institutions and other social and ecological factors.

Mapping deforestation

To understand the drivers as well as the effects of deforestation, geographers use various tools that map the extent and density of tree cover. These include aerial photos, satellite images and other spatial data through time.

The World Agroforestry Centre’s approach takes this a number of steps further. It also uses demographic data, such as population density, which is often bypassed by scientists when mapping change.

The new approach suggests that physical drivers, like rainfall, may not be as important as previously thought.

Finally, the new technique provides a way forward for scientists interested in understanding what drives land use and cover change. It allows them to look at how this process interacts with processes like climate change over large areas and long periods of time.

From a scientific perspective, this helps us better to understand the environment and how humans may be modifying it. This in turn will help those designing land management strategies.

Kenyan case

Our research in Kenya shows that the most important predictor of land use and cover change was population density. Kenya is part of the East African Horn region. Like many other countries in Africa, its population is growing rapidly and is largely devoted to rain-fed subsistence agriculture and pastoralism.

Population growth occurred more rapidly in fertile areas, so the conversion of natural vegetation to agriculture was much higher. In less fertile areas, population growth was much slower, so the conversion was less.

Kenyan farmers and pastoralists are largely unable to acquire new land and are instead forced to intensify their practices on subdivided land.

We were able to detect that as the number of people per square kilometre increased, the amount of natural vegetation declined, because it was being replaced by farm or grazing land.

Climate predictors, such as rainfall and air temperature, were also correlated with the conversion of natural vegetation to agriculture, but less so compared to population density.

The ConversationAs seen in the Kenya case, the growing demand for food in Africa must be met with effective land tenure reform. By mapping changes in our environment continuously over long time periods, farmers and policymakers can understand underlying mechanisms and explore opportunities for reform.

Michael Marshall, Climate Change Scientist, World Agroforestry Centre (ICRAF)

This article was originally published on The Conversation. Read the original article.

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NSW Road Trip 2010: Packing & Getting Ready


It is now the day prior to the NSW Road trip 2010. I have begun packing and getting ready for the journey that lies ahead. I don’t expect to be taking a lot of gear, as I won’t be doing a lot of cooking, washing, etc, on this trip.

I have learnt that it is important to not assume that you have everything you need and then find out the day before that you may not – I already knew this of course, but having recently moved, I no longer have everything that I once did. For example, I do not presently have a sleeping bag. I got rid of the last one because it was old and smelly, and I planned to buy another. But a lot has happened since mid 2007 when I packed to move – including a near fatal car accident that put my purchasing plans well and truly on hold, and they then slipped into the area of my mind that ‘forgets.’

So now I have no sleeping bag – but that isn’t too important as I don’t believe I really need one this time round. It is a road trip, with several cabin stops along the way and only caravan parks with powered sites for the rest. I will take a couple of blankets should I need them (which I don’t believe I will – it will be quite hot in the outback this time of year).

Of course it is not just the sleeping bag that is missing. I am also missing a fly cover for the tent, but thankfully I had two tents so I’m OK there. There are a number of other items missing also, but I don’t really need them this time round. Thankfully I have spotted all this now, which means I can plan to purchase what I need for future adventures, back pack camping, etc. I had of course planned to buy these items, but with the passing of time I forgot.

Anyhow, the packing is under way and I just hope I don’t forget something I wish I had packed when I am on the journey. I’m relatively sure I haven’t – which isn’t to say That I have forgotten something.

What I’d like to remember – and tomorrow I’ll know for sure if I have – is how I packed the car, so that everything was easily accessible. I was fairly well organised for this sort of thing when I was doing it fairly regularly several years ago – but it has been a while. Minimal gear wisely packed, without leaving anything necessary behind – that’s the key for this type of journey and vacation.

This will be the first time however, that I have a bag dedicated to my online activities – laptop, digital camera, web cam, flash drives, etc. I hope to keep an accurate and useful journal online at the kevinswilderness.com website, with photos, comments, route map, etc. So this is a ‘new’ bag that I need to organise in the overall scheme of things.

Anyhow, packing is now underway and coming to a conclusion. The journey will soon kick off.