Water and life
Water, water everywhere, Nor any drop to drink (S. T. Coleridge)
Water supports all life on Earth – including the entire human population, both rich and poor. It is the most important resource on the planet.
Water is also our most abundant resource – but most of it is salt water in the oceans. Of the world’s total water resources, less than 3% is represented by freshwater and less than 1% of that (less than 0.03% of total water) occurs in the Earth's liquid surface fresh water (the remainder is groundwater, below the planet’s surface, or locked in the ice-caps).
The fraction of water available on Earth as fresh water supports a stunningly and disproportionately high level of biodiversity, which includes not only life living within water, but that which depends upon inland water habitat.
For example, although estimates vary, of the 29,000 or so recorded species of fish, about 30% are freshwater species. Taking into account the relative abundance of marine and freshwater habitat, that makes freshwater species diversity around 1000 times higher than marine – on a volume of habitat basis.
Water and human health
The Romans realized, as have every civilized people since, that living in cities is impossible if the water supply is not reliably clean and fresh (F. & F. Chapelle)
As a component of total species diversity, inland water biodiversity is important. But eclipsing this is the importance of inland water biodiversity to human well-being.
Inland water biodiversity is critically important to poverty reduction and the achievement of human development targets. The direct use of inland water biodiversity (e.g., for inland fisheries) provides food security for countless millions of the world’s poor. Moreover, the broader ecosystem services provided by inland water biodiversity, such as climate regulation, flood mitigation, nutrient recycling, water purification and waste treatment, are critical to human welfare and development. Inland water biodiversity is critical to the achievement of most, if not all, of the Millennium Development Goals and their targets. For example: lack of access to safe drinking water is an indicator of poverty - groundwater supplies drinking water to an estimated 1.5-3 billion people – and in most areas groundwater is recharged through functioning wetlands; therefore sustaining its supply is a biodiversity-related issue (and the same could be said for sustaining groundwater-dependent ecosystems such as forests and agricultural areas). Similarly, the remainder of the world’s population relies on surface water – also maintained, to a large degree, by functioning freshwater ecosystems.
to see further discussion on linkages between inland water biodiversity and poverty reduction.
Inland water ecosystems services
We never know the worth of water till the well is dry (T. Fuller)
Inland water biodiversity underpins the provision of most goods and services that freshwater ecosystems provide to people. These are diverse and include not only direct use for food, fibre and medicines but also benefits such as pollution and nutrient absorption and recycling, flood management, drinking-water supply and mitigation against the impacts of natural catastrophes and climate change.
Estimates of the economic value of ecosystem services provided by inlands waters vary widely and, as for other biomes, there is no clear consensus. Results depend greatly on valuation approaches used and particularly the extent to which non-market values are included. Also, it is often difficult to distinguish between the value of water itself and the role of biodiversity in its provisioning. The lack of boundaries to inland water ecosystems
complicate matters: for example, a large percentage of the world’s forested ecosystems, and the services they provide, depend on functioning aquatic environments – such as on the Amazon floodplains.
Conclusions from the Millennium Ecosystem Assessment
give some comparison:
Estimates for the global economic importance of wetlands are highly variable, with an upper value of $15 trillion (over three times the value of global forest ecosystem services, which is $4.7 trillion). Intact wetlands have a net present value of 1.6 times that of sustainable forests, 5.8 times that of mangroves and 4.5 times that of forests under traditional management.
The role of inland waters biodiversity in climate change
One of the most important roles of wetlands is in the regulation of global climate change through sequestering and releasing a major proportion of fixed carbon in the biosphere. For example, although covering only an estimated 3–4% of the world’s land area, peatlands are estimated to hold 540 gigatons of carbon, representing about 1.5% of the total estimated global carbon storage and about 25–30% of that contained in terrestrial vegetation and soils.
Mitigation of climate change
Sea-level rise and increases in storm surges associated with climate change will result in the erosion of shores and habitat, increased salinity of estuaries and freshwater aquifers, altered tidal ranges in rivers and bays, changes in sediment and nutrient transport, and increased coastal flooding and, in turn, could increase the vulnerability of some coastal populations. Wetlands, such as mangroves and river floodplains, play a very significant role in mitigating the impacts of extreme weather events (and natural catastrophes such as Tsunamis).
It is generally understood that removing the existing pressures on wetlands and improving their resilience is the most effective method of coping with the adverse effects of climate change.