In the Sahara desert, if water disappears then so does life.
The problem of desertification across the world's biggest low-latitude hot desert comes down to a combination of climate change and over-exploitation of resources.
The World Day to Combat Desertification started back in 1995. Each year organisers hope to highlight how serious an issue this is.
However, behind the rhetoric, those living in or close to the Sahara want to know what is actually being done.
Many of the people I have spoken to in oasis villages and towns in Tunisia tell me how they watch helplessly as their wells run dry and their land turns into a dusty, salty wasteland. Tens of thousands of palm trees have died or are dying. Those palm trees are not only a barrier to the sand, but also a source of fruit and income.
According to the United Nations, around 850 million people are directly affected by this land erosion.
The town of Hazoua on Algeria's border with Tunisia has shown it is possible to reclaim land once lost to the desert.
The project funded by Germany and the World Development Fund focuses on more sustainable irrigation and salt-resistant plants.
The UN wants to build a similar great green wall across the African continent, spanning thousands of kilometres between Senegal and Djibouti.
This ambitious project has already started and is funded by many investors including the World Bank and the African Union.
There is no doubt that something needs to be done to halt the expanding Sahara desert, which is destroying land and also livelihoods as it spreads north and south.
Source: Al Jazeera