ConservationBytes.com

I admit that I might be stepping out on a bit of a dodgy limb by claiming ‘greatest’ in the title. That’s a big call, and possibly a rather subjective one at that. Regardless, I think it is one of the great conservation tragedies of the Anthropocene, and few people outside of a very specific discipline of conservation ecology seem to be talking about it.

I’m referring to freshwater biodiversity.

I’m no freshwater biodiversity specialist, but I have dabbled from time to time, and my recent readings all suggest that a major crisis is unfolding just beneath our noses. Unfortunately, most people don’t seem to give a rat’s shit about it.

Sure, we can get people riled by rhino and elephant poaching, trophy hunting, coral reefs dying and tropical deforestation, but few really seem to appreciate that the stakes are arguably higher in most freshwater systems.

Global loss of wetlands since 1700

The following facts should scare the shit out of most people. Since about 1700, the world has lost up to about 87% of its wetlands¹, with between 64 and 71% lost in the last century alone. Fuuuuuck.

That’s just wetlands. Rivers and lakes aren’t faring much better. Approximately one half of the combined river length (750,000 km) in the USA is ‘impaired’, largely due to agricultural practices (e.g., seepage, drainage, pollution), and 45% of China’s rivers were moderately to severely polluted according to a 2008 survey. Both measured and modelled data appear to support these trends for much of the world, with the exception of a small fraction of rivers in isolated parts of northern Canada, Russia and Alaska. In fact, 65% of global river discharge (and its supported aquatic habitats) is moderately to highly threatened.

There is a disproportionately diverse biota living in fresh water; in fact, > 125,000 freshwater species have been described (~ 10% of all species on Earth), including a whopping one-third of all vertebrates (~ 18,000 species). Now consider that inland waters (lakes, rivers, streams, etc.) cover < 1% of Earth’s surface, and you have an extraordinary biological diversity packed into a very small space.

Accordingly, approximately 32% of all amphibians (which virtually all require fresh water in which to breed or spend at least part of the life cycle), and 37% of all freshwater fishes are threatened with extinction (as reported in the IUCN Red List). We know precious little about the threat status of freshwater invertebrates, but it’s safe to say that similar proportions are also threatened with extinction (and many have probably already gone extinct before we’ve even described them).

If there was ever a more ideal set of conditions to define as ‘biodiversity hotspots’ (i.e., massive diversity; massive threat), I’m not sure what they are.

It’s a little puzzling then why humanity has trashed such a precious resource for its own needs, let alone all the biodiversity fresh water supports. The corollary is that we’ll probably end up beating nine colours of shit out of each other merely over the lack of abundant fresh water. As former Secretary-General of the United Nations, Kofi Annan, bluntly stated in 2001: “Fierce competition for fresh water may well become a source of conflict and wars in the future.”

We’ve buggered up too much of it already to sustain the growing human population for much longer, so conflict is inevitable. Add in climate-change stress to this mix, and the future is even darker. This only means one thing for freshwater biodiversity — it’s going to get a hell of a lot worse before it gets any better.

¹Other long-term estimates of average loss give 54-57%, but these are likely substantial underestimates.

CJA Bradshaw

Essential reading:

• Davidson NC. 2014. How much wetland has the world lost? Long-term and recent trends in global wetland area. Marine and Freshwater Research 65:934-941. doi:10.1071/MF14173
• Dudgeon D. 2010. Prospects for sustaining freshwater biodiversity in the 21st century: linking ecosystem structure and function. Current Opinion in Environmental Sustainability 2:422-430. doi:10.1016/j.cosust.2010.09.001
• Vörösmarty CJ, et al. 2010. Global threats to human water security and river biodiversity. Nature 467:555-561. doi:10.1038/nature09440