Aridity has long been associated with deserts, but it is no longer a challenge confined to the traditionally dry parts of the world. More regions are experiencing a gradual but lasting shift towards drier conditions because of climate change through human actions. As a consequence, it is changing the way people farm, manage water, protect ecosystems and prepare for future risks.
What is aridity?
Not to be confused with drought – which is a temporary period of unusually low rainfall – aridity is a long-term feature of the climate. It develops over decades as rainfall becomes increasingly unable to keep up with the atmosphere's growing demand for moisture. Once a region becomes more arid, adapting to those new conditions becomes part of everyday life. Because it affects the lives and livelihoods of so many, who all have to adapt to those changing circumstances, it is becoming a shared challenge across international agreements on climate, biodiversity, land degradation and disaster risk reduction.
Simply put, aridity describes how dry a place is over the long term. Scientists measure it by comparing how much rain falls with how much moisture the atmosphere can draw from the land through evaporation and plant transpiration. When that balance shifts over many years, landscapes can gradually transition into drylands.
Today, drylands already cover more than 40 per cent of Earth's land surface, excluding Antarctica, and are home to around 2.3 billion people. If greenhouse gas emissions remain high, that number could grow substantially by the end of the century and potentially even double.
Why does aridity matter for the Rio Conventions and the Sendai Framework?
Perhaps it is better to mix that question up and ask why the Rio Conventions and the Sendai Framework for Disaster Risk Reduction matter for aridity instead. The three Rio Conventions to combat climate change (UNFCCC), biodiversity loss (CBD) and desertification (UNCCD) were established to address different global environmental challenges. In practice, those challenges are closely linked.
As aridity affects the systems people rely on every day – the impacts of which are also interconnected – responding and adapting to aridity requires more than short-term emergency measures. It calls for long-term planning that combines sustainable land management, water governance, climate adaptation and resilient food systems. To achieve that and adapt to arid circumstances, we need reliable monitoring, scientific evidence and the knowledge of Indigenous Peoples and local communities, whose experience can strengthen adaptation strategies.
So, aridity is an example of the connection between the individual yet interlinked challenges of our time for which the three Rio Conventions were established. We can therefore argue that countries can achieve more by aligning national planning across the Rio Conventions instead of treating each issue separately, research shows.
The same logic applies to the Sendai Framework for Disaster Risk Reduction, the global agreement that aims to reduce disaster risks before crises occur. Although aridity itself develops slowly, it increases the likelihood and severity of hazards such as drought, wildfires and dust storms. Better monitoring of long-term drying trends, combined with integrated land and water management, can help countries anticipate risks instead of simply reacting once disasters unfold.
Making adaptation work means looking beyond individual hazards or policy areas. Integrating aridity into existing planning processes can support countries adapting in a more coordinated way through stronger cooperation across institutions, better data and science, sustainable land and water management and adequate financing that also reaches the communities most at risk. It also means ensuring that women, Indigenous Peoples, local communities, persons with disabilities and other underrepresented groups have a meaningful role and voice in adaptation efforts. The consequences of aridity extend well beyond national borders and societies, so the road to implementing solutions should as well.
