Unraveling changes in deltas: Exploring drivers and consequences through the lens of the IPBES conceptual framework.

Deltas have a remarkable capacity to sustain human populations, owing to their productivity and biodiversity. The increasing demand for fertile land and valuable resources in deltas has driven dramatic anthropogenic changes in deltas around the world, resulting in their ecological degradation. To make informed decisions regarding management of land in deltas, it is essential to expand the current understanding of the underlying causes and consequences of delta changes. This knowledge is critical for developing effective spatial solutions to deltas. In this study, we conducted a systematic review of existing literature on delta changes over time and across diverse regions. Utilizing the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) conceptual framework, we sought to identify the driving factors and consequences associated with these changes to gain a deeper understanding. In doing so, we explored (1) differences in study focus among regions, and (2) the causes and effects of delta changes. After reviewing 384 articles, we found that delta-change studies have become increasingly popular over the past two decades, particularly in Northeast Asia, North America, and South Asia. However, Africa, Europe, Southeast Asia, and Oceania, which account for almost 50 % of large deltas worldwide, have had few studies. The most mentioned indirect drivers are demography, economy, and governance, which are strongly linked to land use/cover change and waterway modification. These drivers are also strongly linked to many land changes, particularly forest and wetland loss, in deltas worldwide. We suggest that future research should focus on areas and deltas that are currently underrepresented, especially those in biodiversity hotspots and areas where the population depends heavily on delta ecosystems and associated nature's contributions to people (NCPs).