© Environment Agency

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Many people see a dry riverbed as far less valuable than a flowing river. They can be seen as evidence that increasing droughts and water demands are having negative impacts on our environment. And this can be true – but equally, many rivers worldwide naturally alternate between wet and dry states. In some cases these ‘temporary streams’ dominate river networks, especially in drylands.
Temporary streams experience flowing, ponded and dry states (pictured above, from left to right), creating mosaics of habitat patches with contrasting characteristics. Aquatic and terrestrial species timeshare these habitats, enabling temporary streams to support high biodiversity. We know that species in all ecosystems interact with each other and their environment to provide ecosystem services from which people benefit. But what’s the good of a dry river?

We examine a wide, interdisciplinary literature to find any evidence that temporary streams provide us with ecosystem services: do they deserve a better reputation? We focus on services provided by dry channels, to complement what we already know about how people benefit from flowing streams. We compared temporary streams in hot drylands and those in cooler, more humid regions, as well as those in countries with developed and developing economies, to determine how climate and national wealth affect how people access and value services.

Our results include some surprises. For example, although water – a basic ‘provisioning’ service – is most plentiful when rivers are flowing, digging into the bed during dry phases allows people without access to tap water to collect higher quality drinking water more safely. Dry riverbeds also support unique recreational activities, such as a so-called “dry riverboat race” in Australia (pictured below), and challenging off-road ultramarathons.

© Alli Polin, https://creativecommons.org/licenses/by-sa/2.0/

Our study highlights that temporary streams benefit people even when they are dry, with some unique services made possible by shifts between wet and dry states. However, we need new research to quantify how people’s use of services varies across different regions, and to financially value this service use. Such valuation will motivate much-needed management actions to protect these dynamic ecosystems. In the meantime, it’s time to change our perceptions of temporary streams.