When species lose their natural home

By | 2018-01-12T08:53:36+00:00 January 12th, 2017|Conservation, Ecosystems, Species|0 Comments

“The one process now going on that will take millions of years to correct is the loss of genetic and species diversity by the destruction of natural habitats. This is the folly our descendants are least likely to forgive us.” 

                                                                                                   E.O Wilson

This month, we look at some of the species listed as Vulnerable on the IUCN Red List of Threatened Species*, which serves as a barometer for life on Earth.

What makes these species Vulnerable, and what are some of the key drivers of population decline and extinction?

Habitat loss, degradation and fragmentation is a primary driver of extinction. Human beings have dramatically altered the natural environment over the past few centuries, something accelerated by a lust for natural resources, burgeoning populations, and capital’s insatiable appetite for expansion. For example, since the industrial revolution 32.2% of global forest cover has been lost (1), and if all dams currently planned or under construction are built then natural flows would be lost from 93% of all river volume (2).

It is inevitable that such profound changes to the physical environment have a huge impact on Earth’s other inhabitants, and going back to the understanding of biodiversity elaborated in the previous post, that difference between and amongst species reflects organisms’ adaptations to particular environments, it is easy to comprehend how habitat loss drives species extinction. Put simply, where the environment these species are adapted to live in is suddenly replaced by one in which they are not, they can no longer survive. Indeed, the evolutionary process is, in the main, an incremental one unfolding over thousands of years, and whilst some species show an astonishing ability to quickly adapt to human-altered environments, they are the exception rather than the rule.

One species which has struggled to adapt to dramatic changes to its physical environment has been the Wattled crane, which is now listed as Vulnerable on the IUCN Red List. The Wattled crane stands 6 feet tall and gains its name from the fleshly wattle or caruncle which hangs from the base of the bill. Historically this species populated much of sub-Saharan Africa but it is now limited to 11 countries, and more than half of its estimated population of 6,000-6,300 mature individuals is located in Zambia (3). However, the pressures which have forced this crane’s extinction in other areas of the continent have also caused significant population declines in the countries in which the crane is still resident, and a primary driver of this species’ decline has been the loss and degradation of the flooded grassland habitats on which it depends.

Worldwide, wetland habitats declined in area by approximately 40% between 1970 and 2008 (4), and across Africa wetlands have undergone drastic change, often perceived as an expendable habitat. In the Zambezi river basin, the last main stronghold for Wattled cranes, the main driver of habitat loss has been changes to the hydrological regimes of rivers resulting from dam construction at sites such as Cahora Bassa, Kafue Gorge and Itezhi-Tezhi. Evaporation from dam reservoirs means that mean annual flow of the Zambezi has reduced by more than 11%, and the management of the river and its tributaries for upstream energy supply meant seasonal floods have been of an inadequate volume and duration to sustain a healthy and functioning wetland ecosystem (5), and when floods fail just 3% of Wattled crane pairs will attempt to breed (6).The intimacy of the relationship between the life cycles of the crane and the river’s flood regime meant that populations on the Kafue Flats in Zambia, the single most important wetland for Wattled cranes, declined from more than 3,000 birds in the 1970s to just 1,000 by 2002 (3).

In an attempt to conserve Wattled Cranes and the other species which inhabit wetlands such as the Kafue Flats, Synchronicity Earth partner the International Crane Foundation (ICF) has been working closely with the Zambian Wildlife Authority, conducting surveys and carrying out monitoring to identify the impact of hydropower development on the Kafue ecosystem and how water releases can be timed to mimic natural flows. ICF have also embarked on an ambitious project to remove Mimosa pigra, an invasive species which changes open grassland in natural wetlands into dense thickets (7). In doing so, ICF have a long-term vision of promoting conditions which allow for the restoration and conservation of the Kafue Flats, a Ramsar site that is home not just to a critical population of Wattled Cranes but also more than 470 other species of bird, 20 species of antelope and two national parks (8). Consequently, in restoring natural ecosystem function ICF’s work stands to benefit other species, such as an internationally significant population of African Elephants and the Kafue Lechwe, a subspecies of antelope endemic to this wetland which has experienced an 84.8% decline in population over the past 50 years. Their work is also benefiting local communities who have experienced lower fishery yields and a reduced availability of grazing land as a result of the modified flooding regime (8).

Habitat restoration such as this has a key role to play in combating the extinction crisis as for many species moving away from the ‘red zone’ will mean not just conserving the last remaining islands of habitat, but also actively restoring degraded environments to connect fragmented ecosystems, allowing populations to properly recover and for species to become common and abundant once more. Around the world Synchronicity Earth is partnering with organisations committed to carrying out genuine and effective habitat restoration; from the Mangrove Action Project’s work to restore mangroves in South-East Asia using a community-based model of natural regeneration, to the Wildfowl and Wetland Trust’s efforts to restore Madagascan wetlands, and in turn provide habitats for species pushed towards the brink of extinction, such as the Madagascar Pochard.

Madagascar pochards at captive breeding site

Indeed, if habitat loss is a key driver of extinction, then safeguarding and restoring habitats is a fundamental component of conservation. It cannot be a surprise to us that when the habitats which form the natural homes of Earth’s flora and fauna disappear, so too do they. Present and past rates of habitat destruction are leaving too little space for life, and if continued will force an increasing number of species and ecosystems into extinction, something which would surely be the most sad and permanent legacy of our time on this planet. To paraphrase Jay Inslee, “what is a fish without a river, a bird without a tree to nest in?…it is nothing”. It is extinct.

Sources

1. Adams E.E, 2012, World Forest Area Still on the Decline, Eco-Economy Indicators, Forest Cover, Earth Policy Institute, Accessed 03.01.17, http://www.earth-policy.org/indicators/C56/forests_2012

2. WWF, 2016, Living Planet Index, WWF International, Accessed 03.01.17, http://awsassets.panda.org/downloads/lpr_living_planet_report_2016.pdf

3. BirdLife International, 2017, Species factsheet: Bugeranus carunculatus, Accessed 04.01.17, http://datazone.birdlife.org/species/factsheet/wattled-crane-bugeranus-carunculatus/text

4. Ramsar, 2015, State of the World’s Wetlands and their Services to People: A compilation of recent analyses, Ramsar Briefing Note, March 2015, Accessed 05.01.17] http://www.ramsar.org/sites/default/files/documents/library/bn7e_0.pdf

5. Beilfuss R, 2012, A Risky Climate for Southern African Hydro; Assessing Hydrological Risks and consequences for Zambezi River Basin Dams, International Rivers

6. Chezyuka H, 2006, Approaches to freshwater bird species conservation – Wattled Cranes Bugeranus carunculatus and Shoebill Storks Balaeniceps rex in Zambia, in eds: Boere G.C, Galbraith C.A, Stroud D.A, Waterbirds around the world, The Stationery Office, Edinburgh

7. Rojas-Sandoval J and Acevedo-Rodriguez P, 2013, Mimosa pigra, Invasive Species Compendium, Accessed 04.01.17, http://www.cabi.org/isc/datasheet/34199

8. Collier, U, 2006, Reducing Dam Impacts in the Kafue Flats, International Rivers, Accessed 04.01.17 https://www.internationalrivers.org/resources/reducing-dam-impacts-in-the-kafue-flats-1837

* ® The IUCN Red List of Threatened Species is a registered trade mark of IUCN.