Synergistic fire and floodplain solutions

Wildfires, already a major concern in all continents, are forecast to increase in frequency and intensity, impacting parts of the world not previously affected (including the UK under future climate change). Indeed, 2020 was a record year for wildfires globally, and they are estimated to have cost $13 billion in the USA alone (Reuters December 15, 2020). Poor river management practices have contributed to the increased threat of wildfires by drying floodplains, creating a tinderbox effect. For centuries, humans have modified rivers, typically converting multi-channelled rivers into single, deeper channels. This drains and disconnects floodplains, lowers water tables, increases downstream flood risk, and reduces biodiversity by reducing the variety of riverine environments. Changing our approach to river management can therefore have multiple benefits: reduce fires, reduce flooding and increase biodiversity and ecosystem services.

Since 2010, floodplain restoration theory has begun to move towards reinstating multiple river channels and increasing wetted area to slow flow velocities and encourage groundwater recharge. This has become known as 'Stage 0' restoration because it aims to return rivers to their natural (pre-human intervention) state. Several sites have been set up to test the effectiveness of the approach, notably the South Fork McKenzie River restoration project in Oregon, USA, which started in 2017. One third of the floodplain has been restored to date. A $1.2 million data collection programme was established, running for 3 years so far, which includes monitoring of wildlife and vegetation, on the land and in the water, to assess the effectiveness of the restoration, relative to unrestored parts of the floodplain. The project's success has recently led to similar floodplain restoration trials in the UK, notably on National Trust land in Porlock Vale, Somerset.

Stage 0 restoration has many potential benefits, but until now it has not even been considered in terms of wildfire. However, this changed dramatically in Sept-Nov 2020, when a major wildfire (the 'Holiday Farm Fire') swept through the South Fork McKenzie area, at its peak burning >60,000 ha in 36 hours. The fire only ceased in late Nov 2020, but limited access to the site has recently been granted to the project team. Initial observations strongly suggest that while other parts of the landscape suffered a severe, uniform burn, the restored areas of the floodplain resulted in a diverse fire mosaic, with many parts suffering little or no fire damage. As well as reduced overall burn severity, the more diverse fire intensity in the restored area may actually have biodiversity benefits and build further ecological resilience, according to recent hypotheses in wildfire ecology. The Holiday Farm Fire therefore provides a unique and time-limited opportunity to investigate the ecological and environmental effects of the interaction between wildfire and Stage 0 floodplain restoration. The project site, with 33% of the floodplain restored and the rest as yet unimproved, combined with the detailed baseline data available and a large, very recent fire event, effectively presents us with a natural landscape-scale experiment. We intend to use this amazing opportunity to test the two hypotheses, and to develop both important new understanding of freshwater and terrestrial biodiversity on floodplains, and practical solutions for managing floodplains under both climate change and increasing wildfire risk.