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

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Each year satellite images and maps show patterns linked to land use/cover change.

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.


The attempt to replenish Lake Chad’s water may fail again. Here’s why

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Presidents Issoufou, Yayi, Deby and Buhari at a meeting of the Lake Chad Basin Commission, the body in charge of the lake replenishment project
REUTERS/Afolabi Sotunde

Adegboyega Adeniran, Australian National University and Katherine Daniell, Australian National University

The Transaqua Project is a big, ambitious initiative to replenish the waters of Lake Chad, a fresh water inland lake in Central Africa.

It involves 12 countries working together to build a 2 400 km canal to move about 100 billion cubic metres of water from the River Congo to the lake every year. The Lake Chad basin supports more than 20 million people.

If accomplished, the Transaqua Project will change the face of Africa – for better or for worse. But like other regional or transnational projects on the continent, it may be delayed or abandoned if national politics are ignored.

The replenishment project, mooted over 30 years ago, involves building several dams along the length of the canal.

The dams will potentially generate 15 to 25 thousand million KWh of hydroelectricity and irrigate 50 000 to 70 000 km2 of land in the Sahel zone. This will stimulate development in agriculture, industry, transport and electricity for up to 12 African countries.

But the project is not immune from criticism. Some argue that claims that the lake is shrinking are exaggerated. Others argue that the plan poses serious environmental risks.

It is difficult to determine whether the canal will address why the lake is drying up. And who benefits, and what the benefits will be to each country still remain unknown. It’s also possible that disagreement within and between countries could scuttle the project.

A memorandum of understanding for a feasibility study and the construction of the project was signed in December 2016 by the Lake Chad Basin Commission and PowerChina, the Chinese state engineering and construction firm.

The commission represents the interests of the 12 countries involved in the project and is guided by The Water Charter. This is the main instrument that outlines the mechanisms for dispute settlement.

The Charter, though, focuses on dealing with conflicts between countries rather than within them.

It is therefore worrying that the most important country in the project, Nigeria, faces internal challenges that may affect the project.

The long term nature of the project demands that the participating states are relatively stable in political and economic terms. Nigeria, Cameroon and Libya account for 78% of member contributions to the commission. Libya is currently seen as a failed state, so the focus is on Nigeria to offer political direction for the project.

Nigeria mirrors the challenges

Nigeria plays a powerful role as a regional leader and a major financial member of the Lake Chad Basin. Nigeria also pays 40% of the commission’s membership contributions of €6,275,906.90 (2013 budget).

Three political issues in Nigeria could affect the project.

The first is that President Muhammadu Buhari has had an important influence on its progress. Since he assumed office in May 2015, four milestones have been reached:

  • Nigeria ratified the Water Charter, five years after it was signed.

  • Nigeria signed the Charter for the Lake Chad Basin into law.

  • PowerChina and the Commission signed the memorandum of understanding.

  • PowerChina and Italian firm Bonfica Spa signed a deal to conduct the feasibility study and build the Transaqua project.

If Buhari’s influence wanes, the project could lose momentum.

The second political issue is that Nigerians will go to the polls again in 2019. Buhari’s health challenges, combined with the country’s economic and political challenges, have reduced his approval ratings from 67% when he was elected to 44% in 2016.

The re-organisation and re-emergence of the opposition People’s Democratic Party gives voters a strong alternative, especially in parts of the country without an alternative political party that can compete with their political structure and finances.

That party, which was in power for 16 years, might not be able to meet the financial or security commitments to the water project because of their past history in government.

The third factor relates to institutional politics. The executive secretary of the Lake Chad Basin Commission, Abdullahi Sanusi Imran, has stated that the Transaqua idea “is much more appropriate for the situation of the Lake Chad than all other alternative solutions.” But an informal conversation with a senior Nigerian government official in the course of research fieldwork expressed concern about the choice of the Transaqua idea over other alternatives.

These alternatives were presented in the National Audit Report of Nigeria as part of the Joint Environmental Audit report on the drying up of Lake Chad: a report prepared by the Supreme Audit Institutions of each of the states for the African Organization of Supreme Audit Institutions. Dissenting positions can create unnecessary friction between government agencies and make it difficult to coordinate actions.

So what should come next?

Amendments to the Water Charter to provide for addressing intra-national political challenges are vital; a task for the African Organisation of Supreme Audit Institutions, the Lake Chad Basin Commission and the Supreme Audit Institutions in their respective national domains. States could be required to outline how they might solve potential political challenges in their domains. Expectations and responsibilities should be built into the Charter beyond negotiations and gentleman’s agreements.

The Lake Chad Basin Commission, political office holders and government institutions should work together to make the project’s objectives a key election issue in subsequent elections.

The ConversationIntra-national and national politics cannot be ignored. But the project should also harness local knowledge and experience, and recognise local conditions so that it’s accepted by everyone.

Adegboyega Adeniran, PhD Candidate, Fenner School of Environment and Society, Australian National University and Katherine Daniell, Senior Lecturer, Fenner School of Environment and Society, Australian National University

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