**2. Assessment of land degradation and desertification approaches**

change and associated processes are responsible for around 10% of net global carbon emis‐

One of the main issues in the land degradation and desertification programs is the requirement of robust methods to quantify degradation [2]. The fundamental challenge is providing a reliable account of it, and remote sensor techniques should be reliable and continuous to be a source of information [3–5]. To develop a regional and local mechanism to reverse and prevent degradation, it is imperative then to define monitoring and assessing strategies. The constant and exponential increase of remote sensing technologies offers different options to evaluate phenomena such as land degradation. Organizations dedicated to the production of new remote sensing technologies have implemented new satellite sensors with higher spatial resolution (e.g. IKONOS‐2, QuickBird‐2,SPOT‐5) which indicates a new age of terrestrial

Satellite imagery has been taking information from the Earth's surface for last 40 years in a continuous and reliable way (i.e. Landsat program). Multispectral satellite imagery such as Landsat has opened new avenues for understanding ecological and land cover dynamics [10]. Landsat mission has been collecting imagery since 1972, providing a record of the status and dynamics of the Earth [11, 12]. Changes to policy data in 2008 make free and available the Landsat archive to any user [13]. The free distribution policy increased the supply of imagery dramatically; thus, the use and analysis of the Landsat archive have increased the opportunities

Optical remote sensing has been improved by spatial resolution (pixel size), spectral resolution (number of wavebands), radiometric resolution (sensibility to detect radiation changes), and temporal resolution (data acquisition frequency), which means getting capabilities of meas‐ urement in quasi‐real‐time [14–17]. This scenario opens up the possibility to implement powerful monitoring strategies by taking advantage of the free database policies that many entities have today. Mexico is the perfect example; almost all spatial information is freely available through different government websites. Therefore, some indicators related to degradation are available to be estimated by using remote sensing and ground data. The symbols used are capable, through trajectory or time series analysis, of detecting and mapping

The chapter examines the capabilities of freely available remote sensing, combined with field data, in deriving some degradation indicators. The main idea is the construction of a platform for regional land degradation monitoring and assessment. One of the main assumptions of

IPCC (2013) Intergovernmental Panel on Climate Change. The Physical Science Basis. Contribution of Working Group I

to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

. Land degradation and desertification understood as the loss of productive capacity of the land [1] affect ecosystem productivity, socioeconomic problems, and food security. The UnitedNations through the United Nations Convention to Combat Desertification (UNCCD) seeks to identify and define strategies that support sustainable regional developmentto reverse and prevent desertification and land degradation. The UNCCD works to help countries to improve living conditions of people in drylands and to maintain and restore land and soil

sions1

productivity.

observation and digital mapping [2, 6–9].

4 Land Degradation and Desertification - a Global Crisis

to research in a variety of disciplines [10].

out changes over time.

1

Land degradation, as has been pointed out by the UNCDD, is a global development and environment issue that affects mostly developing countries regarding the economic impact and food security [18]. The assessment and monitoring frameworks developed to provide information about land degradation have been very valuable; however, there are some opportunities to improve and test methodologies according to regional and country needs.

Land degradation and desertification are concepts that are strongly related. Land degradation can be defined as the loss or reduction of the biological production of farmlands, grasslands, forests, and wooded areas and is the result of intense land use or a process (or a combination of the process), including those coming from human actions. It is the outcome of the mismatch between land quality and the intensity of activity part of the actual land use.

According to the UNCCD, land degradation is a complex set of processes of the impoverish‐ ment of terrestrial ecosystem, either natural or human‐induced, that causes the land to be no longer able to sustain its economic functions or the original ecological functions correctly [18]. The consequences of land degradation are land productivity reduction, socio‐economic problems, including uncertainty in food security, migration, and damage to ecosystems.

Desertification, on the other hand, is defined as land degradation occurring in arid‐semiarid and dry sub‐humid areas caused by a combination of climatic factors and human activities. Therefore, only land degradation occurring in drylands is considered as part of a desertifica‐ tion process [19]. As many climatic scenarios have to point out, many areas across the world are vulnerable to climate change because it is going to accelerate the degradation process.
