Don't put all your eggs in 1 basket -- or all your horses on 1 pasture

December 29, 2011

Winters in the Gobi desert are usually long and very cold but the winter of 2009-2010 was particularly severe. Millions of livestock died in Mongolia and the re-introduced wild Przewalski's horse population crashed dramatically. Petra Kaczensky and Chris Walzer from the University of Veterinary Medicine, Vienna have used spatially explicit loss statistics, ranger survey data and GPS telemetry to provide insights into the effect of a catastrophic climate event on wild horses, wild asses and livestock.

In Mongolia, extreme weather conditions - droughts followed by cold and snowy winters - occur at irregular intervals. However, the dzud of 2009/10 was the most extreme winter Mongolia had experienced in the past 50 years. Fifteen out of Mongolia's twenty-one provinces were declared disaster zones and over 7.8 million livestock, 17% of the national stock, are believed to have perished.

Przewalski's horses have been re-introduced intto Mongolia since 1992 and there are now free-ranging populations in Hustai National Park in central Mongolia and in the Great Gobi B Strictly Protected Area (SPA) in south-western Mongolia. Due to its special location at the fringe of the Dzungarian basin, flanked by high mountains, the Great Gobi B SPA received particularly high amounts of snowfall in the winter of 2009/2010. Most snow came with weather from the west and when the snow clouds hit the Altai Mountains on the eastern edge of the Great Gobi B SPA they discharged large amounts of snow, resulting in a strong east-west gradient in snow depth. The high, tightly packed snow made it hard for animals to gain access to the vegetation under the snow.

Herders in and around the Great Gobi B Strictly Protected Area were severely affected by the dzud and lost on average 67% of their livestock. Although herders are semi-nomadic, it was hard for them to escape the worst of the weather as competition for the available winter camps was high. Przewalski's horses were found to use three different winter ranges, two in the east and one in the west. Losses averaged 60% but mainly affected the groups wintering in the east, with the group in the west suffering almost no mortalities. As spatial use of Przewalski's horses is extremely conservative, groups did not attempt to venture beyond their known home ranges. In contrast, Asiatic wild asses seem to have suffered few losses. These animals roam over much larger areas than Przewalski's horses and are not restricted to any particular wintering areas. Petra Kaczensky, the first author on the PLoS paper, says that "wild asses were obviously able to outrun the worst of the dzud by moving west. The long-distance movements and shifts in range highlight how important it is to manage migratory or nomadic species on a landscape level, including multi-use areas outside of protected areas. Fragmentation of their range will reduce their flexibility and can easily result in local population crashes such as the one seen for the Przewalski's horses."

The severe effect of this localized catastrophic event was largely due to the small size and limited range of the present-day Przewalski's horse population. A large and continuous population would be much more robust as it could counteract local population lows or extinctions via re-colonization. The dzud winter of 2009/2010 is a textbook example of how vulnerable small and spatially confined populations are in an environment prone to fluctuations and catastrophes. Losses of this magnitude are difficult to model or predict. As long as populations remain small and spatially confined, their survival cannot be guaranteed, necessitating a long term conservation commitment to ensure the species' future. "The winter disaster really highlighted how dangerous it is to have all our eggs in one basket or in this case all the horses on a single pasture," says Petra Kaczensky. "The national strategy for Przewalski's horse conservation in Mongolia should continue to aim at multiple re-introduction sites with spatially dispersed populations. Ideally the sites should cooperate closely and if necessary also exchange animals on a national as well as international scale. Such steps have already been initiated in Mongolia and the recent downlisting of the Przewalski's horse in the IUCN Red List from 'critically endangered' to 'endangered' shows that this strategy is paying off." Generally, it is not feasible, either technically or financially, to breed and re-introduce all endangered species, as has been done for the Przewalski´s horse. Chris Walzer explains, "More promising strategies involve timely science-based measures to reduce threats to fauna and flora. These may include the establishment of protected areas but it is also important to maintain natural spaces and structures that make multi-purpose landscapes 'permeable' for wildlife, so that wide-ranging species can roam, as Asiatic wild asses tend to do".
-end-


University of Veterinary Medicine -- Vienna

Related Protected Areas Articles from Brightsurf:

Protected areas help waterbirds adapt to climate change
Climate change pushes species distribution areas northward. However, the expansion of species ranges is not self-evident due to e.g. habitat degradation and unsustainable harvesting caused by human activities.

Scientists reveal urgent solutions for boosting Protected Areas effectiveness
New research published today in Nature identifies the actions needed from governments, private entities, and conservation organisations to boost the effectiveness of Protected Areas and other area-based conservation efforts in protecting biodiversity and providing benefits to people.

More than 90% of protected areas are disconnected
Ongoing land clearing for agriculture, mining and urbanisation is isolating and disconnecting Earth's protected natural areas from each other, a new study shows.

Protected areas can 'double' imperilled species populations
A University of Queensland-led research team has revealed that many endangered mammal species are dependent on protected areas, and would likely vanish without them.

Are protected areas effective at maintaining large carnivore populations?
A recent study, led by the University of Helsinki, used a novel combination of statistical methods and an exceptional data set collected by hunters to assess the role of protected areas for carnivore conservation in Finland.

Protected areas worldwide at risk of invasive species
Protected areas across the globe are effectively keeping invasive animals at bay, but the large majority of them are at risk of invasions, finds a involving UCL and led by the Chinese Academy of Science, in a study published in Nature Communications.

Underprotected marine protected areas in a global biodiversity hotspot
Through the assessment of the 1,062 MPAs in the Mediterranean Sea, covering 6% of the Mediterranean Basin, a research team has shown that 95% of the total area protected lacks regulations to reduce human impacts on biodiversity.

Warming climate undoes decades of knowledge of marine protected areas
A new study highlights that tropical coral reef marine reserves can offer little defence in the face of climate change impacts.

Caribbean sharks in need of large marine protected areas
Governments must provide larger spatial protections in the Greater Caribbean for threatened, highly migratory species such as sharks, is the call from a diverse group of marine scientists including Stony Brook University School of Marine and Atmospheric Sciences (SoMAS) PhD Candidate, Oliver Shipley.

Red coral effectively recovers in Mediterranean protected areas
Protection measures of the Marine Protected Areas have enable red coral colonies (Corallium rubrum) to recover partially in the Mediterranean Sea, reaching health levels similar to those of the 1980s in Catalonia and of the 1960s in the Ligurian Sea (Northwestern Italy).

Read More: Protected Areas News and Protected Areas Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.