New research from Australia has confirmed a direct and alarming link between deforestation and large-scale flooding, showing that removing forest cover can increase the likelihood of major floods by as much as 700%. The findings, based on decades of data from regions repeatedly hit by forest fires, mark one of the clearest proofs yet that forest loss directly amplifies flood hazards.
The study, led by Professor Ashish Sharma from UNSW Sydney, analysed flood records and streamflow data from southeastern Australia over the past 50 years. Researchers compared periods before and after three major forest fires in 2003, 2007, and 2009, while carefully excluding years influenced by extreme rainfall events or climate patterns like El Niño and La Niña. Their results revealed that the chance of an extreme flood jumped from one in 64 years to one in eight years after widespread canopy loss.
“In simple terms, there’s an eight-fold increase in flood risk when forests are cleared,” said Prof. Sharma. “If you had 64 catchments with forests, you’d expect one to flood in a given year. But if those forests are removed, eight of them could flood under the same climate conditions.”
The researchers found that the absence of tree canopies and leaf litter, which normally absorb and slow down rainfall, was the primary reason for the increase. Contrary to earlier assumptions, changes in soil structure after fires such as becoming water-repellent were not the main contributors. Instead, it was the direct removal of the forest canopy that caused rainfall to reach the ground more quickly and saturate soils faster, triggering floods.
By comparing severely burned catchments with areas where fires were less intense, the team confirmed that deforested regions experienced stronger and more frequent flooding, while intact forests showed a natural “dampening effect.”
The study’s authors warn that as climate change fuels more frequent and intense wildfires across the globe, flood risks in deforested regions will rise dramatically. Professor Young-Oh Kim from Seoul National University, a co-author, noted that recent mega fires in South Korea highlight similar dangers, reinforcing the study’s relevance worldwide.
The research, published in Communications Earth & Environment emphasizes that forest canopies play a crucial dual role intercepting rain before it hits the ground and dispersing it slowly over time. The leaf litter beneath trees further acts as a sponge, reducing runoff and allowing the soil to absorb more water.
Professor Sharma hopes policymakers and land managers will take note. “Deforestation isn’t just about biodiversity loss it’s a direct threat to human safety,” he said. “Whenever large-scale clearing takes place, there must be strict planning and protection for downstream communities that face the increased danger of flooding.”
The message is clear: cutting down forests today could mean catastrophic floods tomorrow.