UN Secretary-General Antonio Guterres has called it a "moonshot moment": a 12-day meeting for the United Nations Convention to Combat Desertification (UNCCD), looking to protect and restore land and respond to drought amid the onslaught of climate change.

The last such meeting, or "Conference of the Parties" (COP) to the convention, held in Ivory Coast in 2022, produced a commitment to "accelerating the restoration of one billion hectares of degraded land by 2030".

But the UNCCD, which brings together 196 countries and the European Union, now says 1.5 billion hectares (3.7 billion acres) must be restored by decade's end to combat crises including escalating droughts.

A day before the COP16 talks in Saudi Arabia, home to one of the world's biggest deserts, a new UN report warned that forest loss and degraded soils were reducing resilience to climate change and biodiversity loss.

"If we fail to acknowledge the pivotal role of land and take appropriate action, the consequences will ripple through every aspect of life and extend well into the future," UNCCD Executive Secretary Ibrahim Thiaw said in the report.

Land degradation disrupts ecosystems and makes land less productive for agriculture, leading to food shortages and spurring migration.

Land is considered degraded when its productivity has been harmed by human activities like pollution or deforestation. Desertification is an extreme form of degradation.

- 'Vicious cycle' -

Activists accused Saudi Arabia, the world's biggest oil exporter, of trying to water down calls to phase out fossil fuels at last month's COP29 UN climate talks in Azerbaijan.

However, desertification is a perennial issue for the arid kingdom.

"We are a desert country. We are exposed to the harshest mode of land degradation, which is desertification," deputy environment minister Osama Faqeeha told AFP.

Saudi Arabia is aiming to restore 40 million hectares of degraded land, Faqeeha told AFP, without specifying a timeline. He said Riyadh anticipated restoring "several million hectares of land" by 2030.

So far 240,000 hectares have been recovered using measures including a ban on illegal logging and expanding the number of national parks from 19 in 2016 to more than 500, Faqeeha said.

Other ways to restore land include planting trees, crop rotation, managing grazing and restoring wetlands.

"We found ourselves caught in a vicious cycle that we must break," UNCCD executive secretary Ibrahim Thiaw told the conference in Riyadh.

"We can only achieve this if we move beyond the silos that hinder our collective action and if we adopt a holistic approach that recognizes the constant interaction between desertification, biodiversity loss, and the acceleration of climate change."

- 'COP charade' -

Thousands of delegates have registered to attend the December 2-13 COP16 talks in Riyadh, including "close to 100" government ministers, Thiaw said.

The event comes at a parlous time for the COP environmental meetings, which bring together the signatories to various treaties to try to strike new agreements.

Last week the COP29 climate talks in Azerbaijan came to a contentious end, as a pledge of $300 billion to help poorer countries transition to cleaner energy was slammed as too low by developing nations.

On Sunday in Busan, South Korea, deeply divided negotiators missed a deadline to reach a landmark global treaty to curb plastic pollution.

And last month, talks in Colombia -- also called COP16 -- ended without a roadmap to ramp up funding for species protection. They will resume in Rome in February.

Matthew Archer, assistant professor in the Department of Society Studies at Maastricht University and author of "Unsustainable: Measurement, Reporting and the Limits of Corporate Sustainability", was dismissive of the Saudi meeting.

It is part of the "COP charade (that) is totally incapable of facilitating the kind of political action that might sufficiently address the socioecological crises we are facing", he told AFP.

"I wouldn't hold my breath for COP16 to yield a tenable solution to desertification," added Archer.