Whale Poo and Gothenburg Natural History Museum

Hej! I'm in Gothenburg, Sweden this week, and as a Palaeobiology student naturally I made a trip to the Natural History Museum. I have to admit, I had been slightly blinded by London-centrism and forgot that, despite what the London equivalent would have you think, most museums don't require several days to walk around meaningfully. So I was a teensy bit underwhelmed by the size of this museum at first glance. But once inside, I began to see it's charm (not that it's not charming on the outside - set in a huge wooded park within the city). Gothenburg's Natural History museum has the title of holding the world's only mounted blue whale (reportedly - feel free to correct me if I'm wrong). Not only that, once I was stood in front of the thing, I could see that it was mounted on a wooded interior 'skeleton' and contained benches, accessible presumably by the hinged top of it's former skull. Now you can't see that in London.

Mounted blue whale at Gothenburg Natural History Museum. You can just about make out the two rows of blue benches inside.

The importance of whale poo

Recently there's been a lot of news coverage about UK marine megafauna and the 17 key megafauna sites that the Wildlife Trust wants protected along our coastline. (For more on this, you can read this blog post on Ocean Commocean). But what exactly is so newsworthy about these marine megafauna? These animals were fairly untouched in comparison to their contemporaries on land during the Pleistocene extinctions, but over more recent history large marine animals have suffered comparatively unnoticed, due in part to their apparently low commercial value (Lewison et al., 2004). Despite this, they have a big impact on both the marine and terrestrial environment. Whale poo even helps to slow climate change, as discussed in George Monbiot's Conservation blog last month. 

Here's what caught my attention from the post... 

Whales return to the surface to breath and defecate (Lavery et al., 2014). The faeces fertilises the surface water, known as the photic zone - where sunlight penetrates and where photosynthesising plankton live. This iron-rich faeces helps them to grow and multiply.  

In the 1970's, people who wanted more krill suggested that the decline in large whale numbers in the southern oceans would lead to an increase in krill populations. This is called the surplus-yield model (Lavery et al., 2014). They were wrong. Instead krill populations have declined steadily along with the whales. Bad for the whales, bad for the krill and bad for us. So what happened?

By feeding at depth when they dive, then defecating at the surface, the whales are transporting nutrients into the photic zone. Iron, part of the nutrient boost contained in whale poo, is a limiting factor in the southern oceans, and the phytoplankton require it to grow (Smith, 2013). The krill feed on the plankton, and so increased plankton growth supports more krill... On top of this, these photosynthesising plankton collect carbon from the atmosphere, and lock it up for thousands of years when they die and fall to the sea floor. So before their populations began to decline, it's likely whales made a small but significant contribution to the removal of carbon dioxide from the atmosphere. 

From Sciencedaily
Whales are ecosystem engineers. 

Lesson to be learned (again)?

It seems in ecology more and more often we are discovering that we have underestimated the complexity of ecological interactions, and as such our fiddling with parts of the system often results in loss on both sides.

As discussed in my post Trophic Cascades in the Cascade Mountains... , megafauna are key to ecosystem functioning . In the past, ecologists studied ecosystems and found them to be controlled by abiotic factors (climate, geology, nutrients...) rather than by biotic (living) components, such as megafauna. Modern ecology recognises the importance of living components. Large carnivores are particularly vital due to their impact on the populations and behaviour of large herbivores (Monbiot, 2014). These in turn alter the plant community structure and composition, which affects soil erosion, river movement, carbon storage and other processes. So nutrient availability, the shape of the land and atmosphere composition are powerfully affected by living system components.

It seems that the old view came about because the ecologists were studying degraded ecosystems affected by mankind. In a human-impacted system, abiotic factors increasingly rule (Monbiot, 2014). 

Ecosystem connectivity

When humans tip the balance, whales can become part of the problem we created. Roman et al. (2014) suggest that the decline in the great whales (baleen and sperm whales) triggered orcas to switch from feeding on them to seals and sea lions. Then the decline in seals due to (take a guess) human hunting in the Aleutian archipelago, near Alaska, seems to have caused the orcas to switch their diet again to sea otters. 

From seaotters.com
The effect of sea otters on the kelp forest ecosystem. Kelp forests have been described as the rainforests of the oceans. If you're interested there's more info available on the seaotters website

Sea otters, megafauna in their own right, are famous for their part in the kelp forest/ sea urchin trophic cascade disaster, with huge impacts on atmospheric carbon dioxide. 

Sea otters have been heavily hunted along North American coastlines, causing urchins to increase and kelp forests to die. Whales preying on the sea otters, which are now a focus of international conservation efforts, creates another challenge in the restoration of this ecosystem (Monbiot, 2014). 

The video below is from the Planet Earth series, showing the sea urchins in action

Ecosystems are connected more intricately than we often appreciate. This understanding can not only explain some of the mystery behind the megafaunal extinctions of the past, but also help us to understand the ecosystems we have today, and to better protect them to ensure their long time survival as well as our own.

There is so much more in the post by George Monbiot, it's 2000 words long but an easy read so I would encourage you to take a look if you're interested. 

Younger Dryas Impact Hypothesis: Part 3

Phew, finally at Part 3! These are the last two areas of debate surrounding the YDIH I'm going to cover, but there are a few more that go deeper into the geology. The Holliday et al (2014) has quite a bit more on the geology as does the Pinter et al., (2011) paper. 

Megafauna extinctions

Does the YDIH explain the megafauna losses better than human or climate models? As mentioned in Part 1 of this post, the YDIH is claimed to overcome many of the more uncertain aspects of the climate or overkill hypotheses (Firestone et al., 2007). The YDIH, however, also runs into some issues when it is applied to the megafaunal extinctions.

The problem is that a giant impact in North America should, intuitively, cause the highest number of extinctions in North America. Even on the American continent this is not true, with around 50 mammal genera lost in South America and 33 in North America  (Barnosky et al., 2004). 

This problem gets bigger when you consider the extinctions that occurred world wide. Europe, Africa and Australia suffered megafaunal losses (see my Causes of Late Pleistocence Continental Extinctions post!). You could imagine that the impact was big enough to cause these widespread extinctions, but then how did any megafauna survive in North America? The cougar, grey wolf, bison, musk-oxen, elk and tapirs are all end-Pleistocene survivors, to name a few (Holliday et al., 2014). 

These aren't ecologically confined examples either. The survivors from North and South America present a wide range of life histories and ecological niches (Holliday et al., 2014). So it can't be that one environment was less affected, allowing a certain group to survive. 

Moreover, the fact that megafauna survived on Wrangel island, Russia and St. Paul island, Alaska while megafauna on the neighbouring continents did not, doesn't make sense in the context of an impact event (Holliday et al., 2014). 

Clovis decline and cultural shift:

If the megafauna were affected by an impact, then the humans should have been too (note: humans are considered part of the mammalian megafauna group (Barnosky, 2008)). Humans in North America at that time belonged to the Clovis culture (Haynes, 2008). The YDIH suggests that this group underwent an adaptive shift combined with a population decline (Firestone et al., 2007). This is claimed to explain the shift in culture at 12,900 BP, as well as an archaeological gap immediately following the Clovis period in which no human artefacts are found (Firestone et al., 2007).

YDIH proponents point out that sites containing both Clovis and post-Clovis are rare (Firestone et al., 2007), implying a disruption in settlement or landscape use, as the result of an impact. Interpreting this as a population collapse, however, is problematic because most Palaeoindian sites were not re-used (Holliday et al., 2014), and so the majority of these sites, including Clovis, also lack immediately succeeding occupations/ land use. Where multiple occupations do occur at such sites, stratigraphic gaps between them are readily explained by geomorphic processes (Holliday et al., 2014). 

Also, there is an issue with defining exactly what is and what isn't Clovis. Clovis culture is generally defined by the characteristic shape of the arrow heads its people made (Howard, 1990), but even within this (somewhat arbitrary) group there is considerable variation, e.g. between different populations (Smallwood, 2010). 

From Simthsonianmag
Variation in Clovis points

Where Clovis and post-Clovis sites are well defined chronologically (that is, people assign definite time boundaries to the two groups), the archeological and stratigraphic records fail to provide evidence of a population collapse (Holliday et al., 2014). On top of this, calibrated radiocarbon ages show continuous occupation across the time of the impact event rather (Holliday et al., 2014). 

Finally, the apparent end of the Clovis culture is probably actually an evolution of parts of a tool assemblage (a common occurrence in the global archaeological record). It might therefore be hard to argue that a change is tool types is due to an environmental disaster (Holliday et al., 2014). 

So the YDIH may be an unnecessary solution for archaeological problems that don't exist  (Holliday et al., 2014). (And it doesn't really help with the environmental or megafauna problems either)... In summary, a large proportion of the lines of evidence suggested have been non-reproducible (a very bad thing for a scientific theory) (Pinter et al., 2011). The evidence left over seem to be a result of non-catastrophic mechanisms and terrestrial processes (Pinter et al., 2011). There's a fair bit of bad science surrounding the YDIH, so I, personally, am unconvinced. But read around, and decide for yourself. 

Younger Dryas Impact Hypothesis: Part 2

So, following on from my last post, what are some other potential issues with the Younger Dryas Impact Hypothesis? 

Craters

There are no well-dated craters from the end-Pleistocene. However, the impact proponents have argued for: 

A) an impact on the Laurentide ice sheet, which didn't leave a crater due to hitting the ice, or 

B) an airburst explosion that affected the whole continent (and beyond) and left no craters, or 

C) a combination of the two.

The Carolina Bays and playa basins of the Great Plains have been suggested as evidence for an impact around 12,900 BP (Holliday et al., 2014). The bays are elliptical depressions found along the Atlantic Coastal Plain, North America. However, dating now indicates that the bays formed over a period of time throughout the late Pleistocene, but before 12,900 BP (Holliday et al., 2014).

The playas are smaller, and contain water at some times of year. There are over 20,000 of these, and only one has been confirmed as the result of an impact. All others have a roughly horizontal erosional unconformity (a break in the rock layer succession as result of erosion wearing down top layers. Over time, new layers are deposited on top. The surface where these contact is the unconformity) between the playa layer and the older, underlying layers. This is not the geology of an impact site, it's the result of terrestrial geomorphic processes (Holliday et al., 2014).

Ice sheet impact

The impactor may have broken up to produce a scattering of airbursts, starting wildfires across the continent and destabilising the ice sheet (without leaving any crater/s). However, a 4 km wide comet (the size calculated to be needed to cause the widespread environmental changes Firestone et al. (2007) hitting an ice sheet, would shock the rock layers beneath the ice, leaving behind an impact structure of some kind but the record of landforms and sediments left at the ice margin provide no evidence for an impact around 12,900 BP (Holliday et al., 2014).

From: Quaternary Geology
Laurentide Ice Sheet: the larger ice sheet on the right. The one on the left is the Cordilleran Ice Sheet, with the ice free corridor between. This corridor is one of the hypothesised routes of humans into North America

Holliday et al., (2014) state 'the basic physics of the YDIH does not agree with the physics of impacts nor the basic laws of physics'. (Ouch!) The mechanisms suggested for the explosion do not conserve energy or momentum (Holliday et al., 2014). On top of this, they argue that no mechanism is known to create an airburst that would affect an entire continent. 

[This may seem like gobbledygook but I’m sure the physics readers will be nodding along, (at least I hope so). As a non-physicist, you may have to take a leap of faith here along with me: conserving energy and momentum are important laws that things like comets normally are expected to follow.]  

The rest of this argument will be in the final Part 3, since the last part is actually the most interesting in my opinion and it'd be a shame if you were asleep by the time you got there...

Younger Dryas Impact Hypothesis

From: The Subversive Archeologist

(I've tried to link jargon terminology to google definitions of those words, just click on them as you would a reference)

The Younger Dryas impact hypothesis (YDIH) proposes that at around 12,900 cal a BP (calibrated date), North America was subject to an extraterrestrial impact event. This event is hypothesised to be responsible for the end Pleistocene environmental changes such as the Younger Dryas cooling, huge wildfires, the extinction of late Pleistocene megafauna, and the end of the Clovis culture (Holliday et al., 2014). 

[Younger Dryas cooling: a period of rapid cooling of the North Atlantic and a weakening of the Northern Hemisphere monsoon. The reduction in heat moving north resulted in a warmer Southern Hemisphere. The cooling is widely thought to be a result of a slowing of the Atlantic meridional overturning circulation, AMOC. However, the forcing behind this is debated] (Carlson, 2010)

The YDIH is argued to overcome many of the shortfalls of the overkill and abrupt environmental change hypotheses - see my previous posts! (Firestone et al., 2007) (Holliday et al., 2014). For example, the lack of kill sites for 33 genera of now extinct megafauna, including camels and ground sloths, has been identified as a problem with the overkill hypothesis. The fact that similar environmental shifts occurred throughout the Pleistocene but the extinctions only occur at the end of this period has likewise been highlighted as a flaw in the climate shift theory (Firestone et al., 2007). 

Firestone et al. (2007) suggest evidence for the YDIH includes: 

1. The discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules; all attributed to cosmic impacts/ mid-air explosions.
2. A carbon rich deposit overlying Clovis-age sites in North America.
3. The impact's apparent coincidence with the onset of Younger Dryas cooling, caused by the destabilisation of the Laurentide ice sheet as a result of the impact.
4. Bones of megafauna and Clovis tool assemblages have been reported to occur below this layer only.

Despite this, the YDIH has fallen out of favour more recently. Here I'll outline some arguments against the markers and carbon deposit lines of evidence.

LeCompte et al. (2012) state that morphological and geochemical analyses of the microspherules (see this post on the Earth Science Eratics blog for more about spherules) suggest they are not cosmic, volcanic, authigenic (a deposit formed where it's found), or anthropogenic in origin. The spherules were found to be similar in composition to terrestrial metamorphic rocks and very different from those formed by cosmic or authigenic processes. 

They appear to have formed by the rapid melting, then quenching of terrestrial materials. LeCompte et al. (2012) describe spherules occurring above the Clovis artifacts with a significant drop below, implying that they were deposited on top of the artifacts at the surface. This implies an impact/ explosion event left behind a spherule layer, after which the humans and megafauna are absent.   

From LeCompte et al. (2012) 

Spherules from the Younger Dryas boundary, at three sites sampled. Topper and BWD (Blackwater Draw) sites are discussed further below. White numbers indicate the diameter of the spherules in microns

Holliday et al., (2014) pose a strong argument against the YDIH. They point out that the stratigraphic, depositional and pedogenic (soil related) contexts of the YDIH have rarely been addressed. But they probably have a significant effect on the record of indicators of impacts (Holliday et al., 2014)

The sedimentological and geochemical data used in support of the YDIH are: 

• Changes in the rates of sedimentation (magnetic microspherules, nanodiamonds and other features of cosmic dust regularly fall on Earth) (Holliday et al., 2014)
• The nature of the depositional environments
• Discontinuities/ breaks in the rock record created by erosion. The carbon rich layer, according to Holliday et al., (2014) represents stability following more rapid/ energetic sedimentation. 

Translocation is a common soil process, where water moving through a soil moves particulates and solutes. These can then accumulate, the accumulation increasing with depth (Holliday et al., 2014, see p.523 for an explanation of this).

Spherules were present in all samples collected from Blackwater Draw and Topper (LeCompte et al., 2012, see figure above). Samples collected below and above the highest concentration of spherules still contained high numbers of spherules (Holliday et al., 2014) (see also Firestone et al., 2007, figure 1). 

Magnetic microspherules and magnetic grains are <500mm to <2mm (Firestone et al., 2007) and nanodiamonds are 2–300 nm (typical of translocated materials). These particulates increase in frequency with depth in the carbon rich layer at Blackwater Draw and Topper (LeCompte et al., 2012, figures 3 and 4) 

The spherules, magnetic grains and nanodiamonds may therefore be affected by translocation and accumulation in the soil. If these markers used to identify the YDB (Younger Dryas Boundary) are present in other sediments as well, then they probably can't be used as reliable indicators of an impact event. They may have accumulated in a layer due to translocation rather than deposition at the surface after an impact/ explosion.

Also, the layer of spheres was 4 cm thick and buried by only 50 cm of sand. This suggests that either: 

1. All the sand from just below the Clovis artifacts to near the surface was deposited with spheres and the amount of spheres depends on the rate of sand deposition, or
2. The spheres were translocated downward and accumulated at the lithologic break created by the artifacts.

Therefore, the Younger Dryas boundary zones used to support the YDIH are in depositional environments that either A) select for the microscopic indicators by being low energy environments (lakes and marshes) compared with immediately underlying high-energy alluvium (riverine) or, B) the indicators are from soils that represent landscape stability over a long time, therefore concentrating those materials

Next post: the arguments against the ice sheet destabilisation, human cultural shifts/ population decline and the link to megafaunal extinctions

Pleistocene rewilding

Something that often crops up when lamenting the lost megafauna is Pleistocene rewilding, where the ecosystems of that era are re-created by reintroducting the lost species (if they still exist elsewhere e.g. grey wolves) or substituting with a close genetic relative if the species is extinct (e.g., African elephants in the place of mammoths and mastodonts).

The ethics and science of this can be tricky. Taking wild animals from Africa or Asia and moving them to areas like Europe or North American has been called a kind of 'biopiracy' (Levy, 2011). Taking animals from captivity and releasing them into such areas is less ethically troubling, and could contribute to a transition from 'zoos' to 'zoo reserves' in unprotected habitats via zoo coalitions as suggested by (Conway, 2003).

The impacts of introducing close matches rather than the real deal is, however, understudied and thus their hypothetical effect on ecosystem remains largely unknown (Levy, 2011). Reintroducing regionally extinct species however is much more popular and well studied (for example, see my post about wolf reintroduction in Yellowstone, US below).

Video from a post in The Scientist. See the post by Daniel Cossins here.

Note: In this video, they mention Aurochs, which are technically extinct (Levy, 2011). However, this may be a case of a close genetic substitution. For example, the aesthetically similar Heck cattle have been used as Auroch stand-ins at Oostvaaderplassen (a European reserve). The 'wild' horses too, are not the same species as those that lived during the Pleistocene, but species such as Konik horses fill similar ecological roles (Levy, 2011).

Causes of Late Pleistocene Continental Extinctions

Island extinctions since the Late Pleistocene were almost undeniably caused by humans, but what happened on the continents is much less clear. A meta-study (giant compilation and review of other studies) by Barnosky et al. (2004), assessed the role of humans and climate on each continent. Perhaps predictably, the dichotomy between humans/ climate and megafauna extinctions has been challenged more recently, as can be seen in this paper as well as in Koch and Barnoksy (2006) The State of The Debate.

Summary of the numbers of megafaunal genera that went extinct on each continent, the strength of the extinction chronology and a comparison of the timing of extinction with the arrival of humans and late Pleistocene climatic change.
From Barnosky et al. (2004)

Eurasia falls in the middle of the extinction body count with 9 genera extinct. Humans are thought to have arrived here around >30ky ago (Raff & Bolnick, 2014). The extinctions were found to be mainly climate induced, with only partial blame falling on the humans. However, this continent stands out in having provisional chronological data points.

Evidence from palaeontology, climatology, archaeology and ecology now supports the idea that humans contributed to extinctions on some continents, but human hunting was not solely responsible for the pattern of extinction everywhere (Barnosky et al., 2004). 

Barnosky et al.'s 2004 paper suggests that the intersect of human impacts and climatic change drove the precise timing and geography of extinction in the Northern Hemisphere. In North America, the 33 genera that went extinct are thought to be mostly down to humans. Humans arrived here around 11.5 ky (thousand years ago) (Barnosky et al., 2004), with climate change beginning prior to human arrival.

South America lost a staggering 50 genera of megafauna, but the mechanism behind this needs more work, according to the paper, to come to a conclusion. Humans arrived here from 12.5ky according to Barnosky, but if settlers took a different route down the Americas, as suggested by Misarti et al. (2012) then this could change the debate, i.e., if people took the Pacific route then they might have arrived in South America much earlier.

'A hypothetical scenario for the peopling of the Americas, showing possible migration events (a–e) coloured according to putative region of origin (Beringia, blue; Siberia, shades of purple). 

 Shading depicts the extent of Beringia during the Last Glacial Maximum. (kyr, thousand years ago.)'

From Raff & Bolnick (2014)

The Southern hemisphere was found to be generally lacking in data. While new evidence from Australia suggests humans helped cause extinctions there, the correlation with climate is weak or untested. Here, 21 genera went extinct. Africa was also found to be in need of more data, with 8 genera extinct and humans appearing around 160ky.

So what does this pattern say about human induced extinctions? It would seem to roughly follow the path of human expansion, with increasingly high death tolls further away from Africa. Previously studies have suggested that this is down to the animals in new places being unaware/ unprepared for humanity, and therefore unable to defend themselves (Martin and Klein, 1984).

However, in North America alone this can be shown to be a shaky assertion. Why did humans tip the balance, when previously arriving predators such as the lion (Pathera leo atrox) and grey wolf (Canis lupus) hadn’t? It's possible it was due to their omnivory and prey switching, combined with an ability to avoid predation from the resident carnivores by using weapons/ dogs/ language (Ripple and Valkenburgh, 2010). According to Ripple & Valkenburgh (2010), humans played a different role within the large-predator guild. Unlike other mammalian carnivore systems, in which interspecific competition is known to affect species densities, humans were omnivorous and probably less subject to intraguild predation, allowing their numbers to increase independently of large-carnivore densities

In order to better understand the details of the late Pleistocene extinctions globally and the population dynamics of the species involves, more realistic ecological models, established chronologies and insight into region-level paleoecology of the time are required. (Barnosky et al., 2004) 

Rhino Poaching Crisis conference and the Woolly Rhino

Did you know the collective noun for a group of rhinos is a crash (TheAlmightyGuru-Animal Groups)? Rhinos are recognisable by their massive bodies, stumpy legs and one or two dermal horns, made out of keratin (the same stuff as your hair and nails) (WWF rhino).  

There are five extant species of rhino: 

1. The White Rhino (Ceratotherium simum) which has two sub species: the Southern White Rhino and the Northern White Rhino

2. The Black Rhino (Diceros bicornis) (split into four sub species) 

3. Greater One Horned  (Rhinoceros unicornis)

4. The Javan Rhinoceros (Rhinoceros sondaicus) 

5. The Sumatran Rhinoceros (Dicerorhinus sumatrensis) (WWF rhino). 

From wikicommons

All species of rhinoceros are under threat of extinction (for example, see IUCN Javan Rhino), through habitat loss and poaching for sale on a highly lucrative black market. Their horns are valued for use in traditional medicine in parts of Asia, especially in Vietnam.


There are moves to change this attitude, see this video with the Duke of Cambridge, David Beckham and Yao Ming. A sad update to the info in this video - there are now only 4 Northern White rhino left, not 7 (WWF rhino).

At the ZSL Rhino Poaching Crisis conference, multiple angles were discussed as to what can be done to save these modern megafauna. One speaker took the attitude that low tech approaches with better paid and provisioned rangers was the way forward (some work in appalling conditions - how can they be expected to risk their lives each day when they aren't even provided with beds at night or basic washing facilities? Unhappy rangers is surely a recipe for disaster). 

She also cautioned that the small pockets of rhinos would be lost, and it was vital to concentrate on the stronghold populations. 

Others talked about the veterinary interventions that in a very small number of cases (i.e., 1 or 2) had managed to save a rhino that was found just after it had been attacked. You can see the video of an individual that's just been found after an attack here  - however, please be warned it is graphic, horrifying and deeply saddening. It's linked rather than included in this post so you can choose whether to see or not. 

More economically-minded approaches were also discussed by Jonathan Baillie (Head of ZSL conservation operations), centering on an impact bond that is only paid to the groups doing the conserving when they meet result based targets. And while I have to admit most of this section went slightly over my head, it seemed like a very people-focused way of funding rhino conservation, which is probably a more efficient way of getting a wider audience on board. 

From thehulkangre.deviantart

While many species of rhino today are critically endangered, the Late Pleistocene also saw the extinction of the Woolly Rhino (Coelodonta antiquitatis) from Europe. In an analysis by (Barnosky et al, 2004), the 9 genera of megafauna that went extinct in Europe at this time can be mostly attributed to climate change. The Woolly Rhino was 3 - 3.8m long, and somewhere around 2,700-3,200kg (Twilight Beasts). Growing to 2m tall, the Woolly Rhino was comparable to the extant White Rhino. It had thick fur and the characteristic stocky short legs seen in rhinos today (Twilight Beasts). It has probably been depicted in cave paintings in Europe, although identification of the Woolly Rhino from these images is debatable due to artistic license and varying skill/ age of the painter (Bednarik, 2008). They are also known from specimens mummified in Siberia (Twilight Beasts). They evolved around 3.6 million years ago in Tibet and subsequently expanded across Siberia and Europe. See the Twilight Beasts post for more about their habitats are distribution. 

The rhino poaching crisis is escalating, and we risk losing the species we have today if the demand for their horn doesn't decrease. Trade in rhino horn is now a major criminal activity, with organised syndicates getting rich on the destruction. In you're interested, see a great infographic by WWF here.

The criminals will be the ones who ultimately benefit from the poaching, while the rest of us, including the consumers of this product, lose out with the disappearance of this charismatic, vital piece of wildlife and no actual medical benefit. For something a bit more fun, see this awesome rhino conservation + martial arts video by Jackie Chan, actor turned conservation advocate.  

Trophic cascades in the Cascade Mountains: top-down forcing and wolf reintroduction

Pleistocene North America was lorded over by megafauna such as the dire wolf, American lion and sabertooth cats, along with the more familiar grey wolf and cougar. These predators filled important, apex, roles in their ecosystems.

Top-down versus bottom-up control of ecosystems is an ongoing debate in ecology, although there is considerable empirical evidence for top-down control (Ripple and Valkenburgh, 2010). Ripple and Valkenburgh (2010) argue that this was the case in Pleistocene North America, operating in a trophic cascade system. The predators have effects that cascade to lower trophic levels and eventually effect primary producers.

Previously, it was put forward by Janzen (1983) that humans had help from these predators in causing extinctions. Ripple and Valkenburgh (2010) argue for the opposite, that predators, operating within a cascading top-down process, had help from humans.

“The top-down hypothesis is based on the premise that the arrival of the first humans as hunters and scavengers in the New World at the end of the Pleistocene triggered a sequential collapse of large herbivores and their predators.”

Ripple and Valkenburgh, 2010

Unlike other mammalian carnivore systems, in which interspecific competition (competition between species) is known to affect species densities, humans were omnivorous and probably less subject to 'intraguild predation' (being eaten by other predators), allowing their numbers to increase independently of large-carnivore densities (Ripple and Valkenburgh, 2010).

The trophic cascade with top-down control theory has been pointed to as a benefit of grey wolf reintroduction into areas such as the (aptly named) Cascade Mountains in the USA, Scottish Highlands and mountainous areas of Western Europe. The successful reintroduction of wolves to Yellowstone National Park, USA, has restored diversity, especially with regards to the primary producers which were previously overgrazed by high numbers of herbivores, particularly elk (Cervus elaphus) (Ripple and Beschta, 2012).

There are two main ways in which wolves (and predators in general) influence ecosystems through their effects on herbivores:

(1) Lethal (density-mediated) effects:

by killing herbivores and, therefore, reducing grazing pressure.

(2) Nonlethal (behaviourally-mediated) effects:

by altering foraging patterns and habitat use of herbivores under risk of predation (Ripple and Beschta, 2007). Also called landscapes of fear, (for example see  Laundré et al. (2010)) herbivores in fear of being eaten avoid certain areas where they are more likely to be eaten, affecting ecosystem structure, composition and function.

From Ripple and Beschta (2012):
'Comparison photographs taken in 1997, 2001, and 2010 near the confluence of Soda Butte Creek with the Lamar River illustrating the stature of willow plants during suppression (A) from long-term browsing and their release (B and C) following wolf reintroduction in the winters of 1995–1996. As of 2010, both willow height and canopy cover increased compared to the earlier dates.'

A long term study by Callan et al. (2013) of recolonizing wolves in Wisconsin, USA, found that forb and shrub species richness at local scales was significantly higher in high wolf areas. This is consistent with the predicted trophic effects on understory plant communities triggered by a keystone predator, recovering from regional extinction as the grey wolf currently is (Callan et al., 2013).  

Prehistoric policy needs updating: Modern megafauna extermination

Okay, so I was wrong about the rhino conference. Turns out I have as good a grasp on time as most other students, so I will be saving that post until next week (when the conference actually is). Slightly sidetracking from Pleistocene extinctions, I thought I should highlight the plight of some modern megafauna… 

In a press release last month, the Centre for Biological Diversity, a U.S. nonprofit charity, revealed the recipient of their national Rubber Dodo award. Proudly continuing the traditions of their forebearers, the U.S. Department of Agriculture’s Wildlife Services has been awarded this year’s Annual Rubber Dodo award, given to those who have done the most to drive species extinct. The program killed more than 2 million native animals in 2013 (up 30% on 2012). This amounts to a horrifying tally of 320 grey wolves, 75,000 coyotes, 419 black bears plus many other animals (Centre for Biological Diversity).

Why has this government department decided to rediscover its roots and ramp up its megafauna killing campaign? National politics and individual gain, obviously. Most of Wildlife Services’ killing is done on behalf of the livestock and agriculture industries (Centre for Biological Diversity).

The methods include aerial gunning, traps and exploding cyanide caps (Centre for Biological Diversity). Is it so difficult to imagine Pleistocene North American settlers foreshadowing this megafauna onslaught with ancient traps, snares, spears, atlatls, bone knives and hand axes? Of course that is just speculation, but it is a sobering thought.

8th Rubber Dodo award for killing megafauna and other wildlife
From Centre for Biological Diversity

“No other government program does more every day to annihilate America’s wildlife than Wildlife Services,” said Kierán Suckling, the Center’s executive director. “This rogue program does much of its dirty work far from the public’s view, so millions of animals disappear from our landscapes every year with little accountability.”

From personal experience, many people living in North America often want to preserve their wildlife, and a series of petitions by locals in Newark, New Jersey saw the halt of a planned bear cull (at least, this was the case last time I visited). It’s baffling and saddening then that the American government of Wildlife Services in particular "...seems to delight in the endless slaughter of coyotes, wolves, bears, beavers and countless birds,” Suckling said. “It’s a shameful legacy that should have no place in American government in the 21st century.”

This of course is the official account that says nothing about the “shoot, shovel and shut up” attitude to wolves seemingly prevalent in the gun wielding denizens of Washington State, on the front line of reestablishing wolf populations (and no doubt other areas). While illegal, the locals interviewed in this programme were not shy about their intentions toward wolves – see Land of the Lost Wolves Episode 1:  available for 8 more days! 

It's possible that there was some element of dramatisation in the selection of interviewees with more extreme (okay, incredibly extreme) views. I hope this is the case and that it's not a symptom of wider spread intolerance towards these awe-inspiring animals.

In fact, the grey wolf is making a tenuous comeback in the Washington region of the Cascade Mountain range. The Lookout Pack, (see the documentary above and find out more here) was the first wolf pack seen in the Cascades in more than 70 years. Subsequently, they were slaughtered illegally by local poachers, seemingly because the wolves competed with them for game. The Cascades are in need of an apex predator to naturally restore balance to its ecosystem, as seen after wolves returned to Yellowstone National Park (Manning et al., 2009). There is, however, a potential conflicting interest of wolves and cougars. The cougars have become the dominant predator of the local prey species, and as it is an endangered species itself, the effect of wolf introduction on cougar populations will have to be carefully monitored...

Grey Wolf (left) in comaprison with it's Dire Wolf cousin (right)
From DireWolfProject 

I have an awful lot to say about wolves so to do them justice, I’ll talk about why wolves, both extant and extinct, are such key components of their ecosystems in the next post, and the consequences of their absence, both in the Pleistocene and relatively recently.