Sustaining Freshwater Biodiversity in the Anthropocene

Abstract

Globally, fresh water is a limited resource, covering only about 0.8 % of the world’s surface area. With over 126,000 species living in its ecosystems, freshwater harbours a disproportionate share of the planet’s biodiversity; it is essential for life, and central to satisfying human development needs. However, as we enter the Anthropocene, multiple threats are affecting freshwater systems at a global scale. The combined challenges of an increasing need for water from a growing and wealthier human population, and the uncertainty of how to adapt to definite but unpredictable climate change, significantly add to this stress. It is imperative that landscape managers and policy-makers think carefully about strategic adaptive management of freshwater systems in order to both effectively conserve natural ecosystems, and the plants and animals that live within, and continue to supply human populations with the freshwater benefits they need. Maintaining freshwater biodiversity is necessary to ensure the functioning of freshwater ecosystems and thereby secure the benefits they can provide for people. Thus freshwater biodiversity is also an important element of viable economic alternatives for the sustainable use of the freshwater ecosystems natural capital. In order to achieve this we need to do a better job at monitoring our freshwater biodiversity, understanding how the ecosystems function, and evaluating what that means in terms of service delivery.

Appendix

Box 1: Balancing Development and Biodiversity Conservation

The Kihansi dam generates about 20 % of Tanzania’s electricity. It is located in the Udzungwa Mountains, where the Kihansi River plunges off an escarpment. Because of its steep drop and dependable water flow, it was selected to develop a hydropower project that was started in 1994. Before the dam was completed, biological surveys of the area yielded the discovery of several species new to science, most famously the Kihansi spray toad (Nectophrynoides asperginis), which was endemic to a very small area of about 2 ha in the spray zone of the Kihansi Falls, the smallest distribution known for a vertebrate (Poynton et al. 1998).

As a result of these biological findings, the government agreed to let 10 % of the river flow to continue its original course—a reduction from over 16 to about 2 m³/s (Rija et al. 2011); this reduced flow proved insufficient to maintain the mist zone that created the toad’s habitat. In combination with other events, such as a one-time flushing of pesticide-rich sediments accumulated at the dam and the possible occurrence of an amphibian fungal disease (Krajick 2006), the toad’s population crashed from an estimated high of over 20,000 individuals in 2003 to less than five individuals seen in 2004 (Channing et al. 2009). There have been no confirmed records since, and the species has been listed as Extinct in the Wild in the Red List of Threatened Species since 2009.

In 2000, some toads were collected from the field in an attempt to establish a captive breeding programme in the US (Bronx and Toledo zoos) that collaborates extensively with Tanzanian authorities. There have also been attempts to recreate the natural spray zone at the bottom of the gorge by means of an artificial sprinkler system, though it is becoming clear that this may not be sufficient, as some elements of the original ecosystem are still absent—for instance, the waterfall created continuous winds that replenished the area with wet silt (Rija et al. 2011). Since 2010, there are ongoing efforts to try to reintroduce some captive bred toads back into the spray zone of the falls, with the first ones released in 2012, but the road ahead is not easy (Khatibu et al. 2008). Millions of dollars have been spent to try to prevent this species from going extinct and change its Red List status from Extinct in the Wild back to Critically Endangered, which would be a first in recorded history. In spite of this, for many locals the dam is the source of their access to electricity that they cherish, even if it comes at the cost of a little known toad (Photo 17.1).

Photo 17.1

Kihansi spray toad (Nectophrynoides asperginus) © Kurt Buhlmann

Box 2: Rapid Assessment (AquaRAP) Programs for Fresh Waters

Since 1996, 13 Rapid Assessment Programs have been implemented to specifically target freshwater ecosystems, focusing on surveys across watersheds or basins. The AquaRAP program has several objectives, listed by Alonso and Willinck (2011). These include increasing the priority given to conservation of freshwater systems; catalysing multinational, multidisciplinary, collaborative research on freshwater systems that includes training of students; highlighting the importance of systematic research and collections for conservation; and generating a body of reliable data about the selected watersheds.

AquaRAPs have confirmed the fact that our knowledge of biodiversity is woefully low for many parts of the world. Just in Latin America, AquaRAPs have identified 238 new basin and country records for fishes in addition to 105 species new to science. New records have also been identified for number of records for planktonic and benthic organisms, but the numbers are certainly underestimates of the total number of species, since there are often not enough taxonomists working on these groups to allow species identifications.

The conservation and management impacts of AquaRAP have been important, resulting in the creation of new protected areas, and the provision of information and advice that has been used by decision-makers (Alonso and Willinck 2011). Harrison et al. (2011) give several examples of where AquaRAP surveys have provided critical data for biodiversity assessments of African freshwater species, as well as application of information for management decisions. For example, the AquaRAP expedition to the Okavango Delta, Botswana catalyzed a process for resolving conflicts between local fishermen and sport fishermen in the delta.

Box 3: Iconic, Flagship Fishes and River Conservation

Large-bodied river fishes are particularly vulnerable to human impacts arising from overexploitation, pollution, dam construction and habitat alteration because many of them are slow growing and/or late maturing and migratory, and thus apt to encounter a variety of threats or stressors at different times and locations during their lives (reviewed by Dudgeon et al. 2006; see also Limburg and Waldman 2009). Examples include the Mekong giant catfish, the Yangtze paddlefish, African tiger-fishes, sturgeon, salmonids and a variety of other anadromous species. Many of these species have (or had) economic value which contributed to their exploitation and subsequent decline. However, this value also provides an opportunity for species protection that is predicated on the adoption of a payment for ecosystem services (PES) model. One example is provided by Everard and Kataria (2011) who describe the benefits obtained by a local community in the Himalayas of northern India from protection of a large ‘flagship’ fish species in the Western Ramganga River. The golden mahseer (Tor putitora: Cyprinidae), which may exceed 50 kg, is a favoured species for recreational angling. Along with associated cultural and wildlife tourism, angling generates income that creates incentives for protection of intact river systems by the local rural populace. They benefit economically from sustainable mahseer exploitation through catch-and-release fisheries, thereby establishing a PES market involving local people, tour operators and visiting anglers. This PES market is sustainable provided that people can benefit economically to a greater extent than they would through killing of fish for sale and consumption.

As Everard and Kataria (2011) explain, creation of local incentives through PES may be the most effective means for preventing destructive over-exploitation of large fishes. The Western Ramganga River model is potentially transferable to other rivers that support potential flagship fish species. It offers means of supporting regional development through involvement of riparian populations in markets for large, iconic fishes, especially where such species also have symbolic or cultural values. It must be stressed that sharing of the benefits of recreational angling markets is essential to promote self-interested resource stewardship of the type practiced along the Western Ramganga River, because without distribution of the revenues from tourism (for instance, where profits accrue to a few business operators only), local people are unlikely to have any incentive to protect freshwater ecosystems (Photo 17.2).

Photo 17.2

Mekong giant catfish (Pangasianodon gigas) © Zeb Hogan

Box 4: Guardians of the Watershed. Dragonflies as Flagship Species for Water Quality

Dragonflies are employed successfully as indicators of ecosystem health in environmental impact assessments and monitoring programs, particularly in Australia (Bush et al. 2013) and Europe (Sahlen and Ekestubbe 2001). They can be used as environmental sentinels and as the whistleblowers for freshwater health, providing an easy tool not only for environmental impact assessments, but also for freshwater monitoring, carried out by various stakeholder groups. Using dragonflies as a flagship species—beautiful, easy to observe and positively perceived throughout—a monitoring scheme can be applied not only at the level of decision makers and conservationists, but also at the local community level.

Recent projects in Angola and Tanzania, which included stakeholders from various backgrounds, have shown that the general problems of environmental health can also be explained here by using dragonflies as flagship species. Once the connection between the presence of certain species and habitat quality is understood, dragonflies can act as the guardians of the watershed—indicating the quality of the water habitat without the need of expensive or difficult tools or survey protocols (see report at www.speciesconservation.org/case-studies-projects/amani-flatwing/4044 (Photo 17.3).

Photo 17.3

Violet dropwing (Trithemis annulata) © Viola Clausnitzer

Box 5: The Integrated Biodiversity Assessment Tool

The Integrated Biodiversity Assessment Tool (IBAT) for business (https://www.ibatforbusiness.org) has been developed through a partnership between UNEP-WCMC, IUCN, BirdLife International and Conservation International. IBAT is a web based decision support tool that provides planners with access to critical spatial information on conservation priorities (e.g. species, protected areas and key biodiversity areas) to inform decision-making processes with the intent of addressing any potential biodiversity risks associated with a development as early as possible. Hence, IBAT can help its users integrate biodiversity risk assessment into development plans; this reduces potentially costly impacts to critical ecosystems and supports well-informed decisions about where to invest effort in sustainable use and management of natural ecosystems. Commercial users currently support underlying data maintenance and update processes via a subscription service. This tool is currently supported by a number of private and public sector users including 25 extractive companies, and is being updated to include more specific functionality related to freshwater including direct access to data on species and sites as well as summarized indices intended to support existing water risk assessment tools in use by the private sector (e.g. WBCSD’s Global and Local Water Tools). It has been referenced by International Finance Corporation’s safeguard systems and featured as a case study by the International Council on Mining and Metals (ICMM) of good biodiversity practice. A free version for non-commercial users (e.g., governments, NGOs or academics) is also available for conservation planning and research purposes (https://www.ibat-alliance.org/ibat-conservation/).