Earth Observation 4 Land Degradation Neutrality— Part 1: urgency and opportunities
Welcome to the first blog in the series Earth Observation 4 Land Degradation Neutrality. This blog series will be a guide into the use and opportunities of earth observation data in our quest against land degradation. The first blog is an introduction into the urgency of land degradation neutrality and opportunities of earth observation as a tool to monitor processes related to land degradation. The other blogs in the Earth Observation 4 Land Degradation Neutrality series are about the different types of earth observation data, where you can find the data, how you can set up an environmental baseline and examples of the application possibilities.
But first it is important to understand what land degradation is and why it is such an urgent problem. Land degradation is a process induced by humankind that reduces biodiversity and aquatic/terrestrial ecosystem functioning. On a short time frame these actions result in economic benefits while on long time frames the effects are disastrous. Inefficient land management such as deforestation resulting in erosion, excessive water use resulting in desertification or increased use of nutrients resulting in eutrophication all negatively affect the biodiversity, food security and deplete our natural resources. Land degradation is currently harming over 3.3 billion people and it is expected that this number is rapidly growing.
If we do not create sufficient adaptation and mitigation strategies we will continue degrading our lands resulting in forced migration, poverty, political instability and conflicts about resources. We need to shift the way we think about land management and practices to a system in which we recover degraded areas and compensate for losses of productive land. The United Nations Convention to Combat Desertification call this new way of land management and practices Land Degradation Neutrality.
“Land Degradation Neutrality (LDN): A state whereby the amount and quality of land resources, necessary to support ecosystem functions and services and enhance food security, remains stable or increases within specified temporal and spatial scales and ecosystems.” — United Nations Convention to Combat Desertification
Because this is a problem that does not stop at the borders of individual countries the United Nations decided to create an agenda for 2030 with 17 goals called the Sustainable Development Goals (SDG). Multiple SDGs are contributing to LDN but in particular SDG 15.3.
“SDG 15.3: By 2030, combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world” — Sustainable Development Goals
Advantages of earth observation
But how can earth observation help to achieve LDN and report on the progress of SDG 15.3? Before this question can be answered it is important to know what earth observation is and what it can and cannot do. Earth observation is the collection of information about system earth this can be done in situ, airborne and spaceborne. The term earth observation mostly refers to the measurements satellite-based sensors collect but it can also refer to for example in situ flux tower measurements.
The main advantages of using satellite-based sensors are most importantly the scale. There are a lot of satellite products available that cover the whole earth making comparisons of areas possible. Besides scale the revision time of the satellite is of importance ranging from daily data to yearly data. Some satellites missions date back to the 1970 which means that very long consistent time series of certain phenomenon’s are available. The validity of the time series derived from satellite sensors can be cross-checked with in situ datasets or the other way around, it offers a complementary information source. The last benefit of earth observation is that it offers a wide variety of measurements. A few examples of these measurements are: greenness of the vegetation, rainfall, temperature and air quality.
Even though earth observation offers a lot of advantages it probably sounds very expensive to launch a satellite and it certainly is. But over recent years the costs have been decreasing and governments start opening up their data making it freely available for everyone. Currently the amount of open and free data is astonishing but finding the right dataset that suits your needs is still a challenge (see blog 2 in the blog series Earth Observation 4 Land Degradation Neutrality).
Opportunity’s of earth observation
To monitor whether land is degrading, restoring or in equilibrium a standardized method for land degradation assessment is needed. As explained in the previous section earth observation can provide synoptic, past and present at a high spatial resolution with short time interval views. It is an objective, consistent and cost effective measure that can identify anomalous changes. Measuring changes over a long time period gives the opportunity to identify areas that are vulnerable to land degradation which can support informed decision making. There are a few sets of earth observation variables that can function as a proxy for land degradation e.g. land cover change, land productivity and carbon stocks.
Land cover change
Human activities are changing our environment on a large scale and are a consequence of constant pressure. Most land cover changes are a result of allocating people, urban sprawl, tourism, deforestation and the intensification of agricultural areas. A lot of studies have showed that there is a negative relation between land use change and land degradation e.g. Balabanis et al., 2000, Burke and Thornes 2004, Bonet 2004, Sluiter and de jong, 2007. Some harmful land use changes are:
- Abandonment of agricultural land leaving vegetation prone to fire and inducing soil erosion
- Deforestation fragmentating habitats
- Crop intensification resulting in polluted soils
- Urbanization
Land cover changes can be an indicator of future land degradation. However, it is good to keep in mind that not all changes are necessarily degrading the land some changes could indicate recovery or rotation schemes.
Land productivity
The definition of land productivity is the Net Primary Production per unit of area and time. A decrease in land productivity can be an indicator of land degradation. It is estimated that 20% of the earths surface showed a decrease in productivity over time (1999–2013). Land productivity maps alone are not a sole indicator of land degradation. For example increases in productivity can be achieved by using resources (water, fertilizer or soil) from other locations causing land degradation somewhere else. Therefore, it is important to take the context of the degradation into account.
Carbon stocks above and below ground
As mentioned before land use and land cover change have contributed to the degradation of many areas on earth. Degraded soils can sequester less carbon then their healthy variants. Deforestation has a similar effect since cut down trees release their stored carbon. Degraded lands have less capacity to sequester carbon and therefore a decrease in carbon stocks both above and below ground can be an indicator of land degradation. Again careful analysis of the timeseries is of the essence since seasonal carbon variations or regrowth can give misleading signs of land degradation.
Other land status indicators
Indicators such as water bodies, protected areas, land surface temperature, precipitation and evaporation can be a valuable addition when detecting land degradation. There is currently not one variable available that can detect land degradation. A lot of indicators are available but none of them are error proof. Multiple remote sensing products combined with ground validation give the most solid results.
Urgency and opportunity’s
Land degradation is an urgent problem and is increasingly harming people. In order to combat land degradation an objective system to identify and monitor areas at risk is needed. As explained in the previous section earth observation data can provide information about our environment with a synoptic view for past and present phenomenon’s. It is expected that Earth Observation 4 Land Degradation Neutrality is going to be an essential tool to reach the targets set by the United Nations. The following blogs in the series will provide information about earth observation data characteristics, data sources and a case study.
Tutorial and reading tips
- NASA offers free online webinars called ARSET “Applied Remote Sensing Training”. If you are new to earth observation or if you want to learn more about how the data is obtained which sensors are used and potential application possibilities the fundamentals of remote sensing course is a great start. From the 9th of June 2019 NASA is also offering a new advanced webinar series about remote sensing for monitoring land degradation and sustainable cities.
- The Global Land Outlook is an elaborate evidence based report by the United Nations explaining the current problems we face regarding unsustainable land management. A brief introduction into the potential use of earth observation data is given for the topics: food security and agriculture, water resources, biodiversity and soil, energy and climate, urbanization and drylands.
- The ITC department of the University of Twente offers an open database with all launched satellites, all sensors and a calendar with the expected satellite launches.
- GEO the group on earth obervations published a report on how to use earth observation to monitor the different SDGs.
- ESA published the Earth Observation Handbook in 2018 about the role of earth observation in quantifying the seperate SDGs.
- A paper published by Dubovyk et al., (2017) in the European journal of Remote Sensing gives an overview of the role of remote sensing in land degradation assessments.
Dubovyk, O. (2017). The role of remote sensing in land degradation assessments: opportunities and challenges. European Journal of Remote Sensing, 50(1), 601–613. - SDG academy provides free courses about the sustainable development goals.
