Human security is under threat from desertification, land degradation and drought. Combating this threat requires an integrated international response, which is why the theme for this year's World Day to Combat Desertification is 'Conserving land and water = Securing our common future'.

Desertification, land degradation and drought (DLDD) deprive people of food, water and their homes and can undermine security and even trigger conflicts. According to the UN Convention to Combat Desertification (UNCCD), these phenomena have already forced between 17 and 24 million to leave their homes and that number is expected to rise to 200 million by 2050.

In its effort to combat DLDD, the UNCCD is calling for the global creation of short-, medium- and long-term strategies to deal with the scarcity of fertile soil by strengthening ecosystem management through the use of technology, knowledge and engineering concepts.

The term 'desertification' does not refer to the spread of existing deserts, but to the creation of new ones through the degradation of drylands, which cover 40% of the world's land surface. Since dryland desertification can be remedied by using appropriate land management techniques, it is essential to monitor the areas most at risk.

ESA has been working closely with the UNCCD secretariat for more than eight years, developing and demonstrating information services based on satellite Earth observation (EO) technologies to allow a better assessment and monitoring of desertification and land degradation.

EO satellites are able to highlight relevant changes in land use and can provide authorities with an overall picture of key pressures on land, such as burned land due to forest fires, erosion processes and their trends over time.

In 2004, ESA launched a large pilot project called DesertWatch to develop a set of satellite-based information services to monitor and assess the status of land degradation with the support of four of the European countries most affected by desertification – Greece, Italy, Portugal and Turkey.

These satellite data were also combined with in-situ information, processing tools, models and geo-information systems to create standardised and comparable geo-information products that were also used to satisfy UNCCD reporting requirements.

ESA is currently preparing an extension to DesertWatch to review and adapt the methodology developed during the first project so it can be applied globally, for the benefit of all UNCCD Contracting Parties. The new methodology will be demonstrated in Portugal, Brazil and Mozambique.

ESA, through its TIGER initiative, is also supporting African countries to overcome water-related problems, such as drought, and to bridge gaps in information related to water through the use of EO technology. Under the first phase of TIGER, ESA provided more than 8500 satellite-based products free of charge to African researchers working on water-related research activities and management projects.

At the request of African water authorities, ESA has extended the initiative. TIGER II will support African efforts to develop sustainable observation systems by using EO technology that will help to establish a sound scientific basis for developing effective adaptation or mitigation measures against the impacts of climate change.

This year's official observance of the World Day to Combat Desertification is being held in Bonn, Germany. ESA will attend the ceremony to highlight the role of satellites in reversing desertification and land degradation.