Cascading planetary-wide ecosystem effects of the extirpation of apex predatory Krayt dragons on Tatooine

Author’s note: this post is part of the “Science of Tatooine” blog carnival. Though obviously about science fiction and not the real world, it includes real ecological theories,  and it uses some real peer-reviewed scientific papers as references. Whenever possible, I’ve linked to accessible copies of those papers and explainers of these ecological terms. Many of the same issues are associated with shark population declines. 

ABSTRACT

Predators play an important role in structuring ecosystems, with predator population declines being linked to a variety of negative ecological effects. Here, we present evidence that the planet Tatooine, famous throughout the Galaxy for being a desert planet, experienced desertification as a result of unintended changes in herbivore populations caused by the intentional large-scale killing of apex predators by offworld colonists. Fossil evidence and interviews showing traditional ecological knowledge suggest that once-abundant Krayt dragons were hunted to near extinction by early human colonists. As a result of the decline in predation, populations of large herbivorous banthas populations grew out of control and overgrazed the plants once found throughout Tatooine.

INTRODUCTION

Studies of numerous ecosystems have consistently shown the importance of intact populations predators to healthy ecosystems, with a recent review (Estes et al. 2011 “trophic downgrading of planet Earth”) noting that “the loss of apex consumers is arguably humankind’s most pervasive influence on the natural world.” Population declines of top predators can cause a trophic cascade, resulting in unintended consequences that ripple through a food chain. Sea otter population declines in the Pacific Northwest of the United States resulted in predation release of otter prey (sea urchins), and an overabundance of sea urchins destroyed entire kelp forest ecosystems by overgrazing (Estes et al. 1998 “killer whale predation on sea otters linking oceanic and nearshore systems.) Wolf population declines in Yellowstone National Park resulted in predation release of wolf prey (elk,) and an overabundance of elk destroyed aspen pine forests by overgrazing (Ripple et al. 2011 “trophic cascades among wolves, elk, and aspen on Yellowstone National Park’s northern range.”)  Ecosystem-wide effects stemming from the loss of predators has also been listed as the proximate cause of disease outbreaks (Pongsiri et al. 2009 “biodiversity loss affects global disease ecology,”), increasing destructive wildfires (Perrings et al. 1997 “biodiversity resilience and the control of ecological-economic systems: the case of fire-driven rangelands,”) and overall biodiversity loss (Paine 1969, “Pisaster-tegular interaction: prey patches, predator food preference, and intertidal community structure.”)

Though the planet Tatooine in the Tatoo system of the Outer Rim is known by researchers to have once been covered by oceans and lush vegetation, it is commonly known now as a desert planet (source). While it is famous in Republic circles primarily for being the home of Jedi Master Skywalker, Tatooine also has native sentient species, including Jawas and Tusken Raiders (the latter are derisively referred to by locals as “sand people” ).  Native non-sentient animals include banthas (large herbivores used as beasts of burden) and the now mostly extinct Krayt dragon (a large predatory species that fed on banthas).

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Halloween Science: Fear Makes the Ocean Go Around

Halloween, in a lot of ways, is a celebration of fear.  We dress like ghosts, goblins, and movie serial killers to give ourselves a sense of control over the things we’re afraid of.  It’s also a good time of year to indulge in horror movies, where we can watch ghosts, goblins, and serial killers terrorize other people from the apparent safety of our own homes.

From an ecological standpoint, we have it pretty good.  We’ve more or less tamed most environments on land and only make short forays into the oceans under conditions where we still have quite a few advantages.  Most of the time we have more in common with Jason than his hapless victims.  Imagine being a member of a school of menhaden or a seal that has to make daily trips through Shark Alley.  It would be like spending your whole life as a camp counselor at Crystal Lake, constantly looking over your shoulder and getting picked off the second you let your guard down.  If mortal terror was a regular part of your life, you’d better believe it would affect your daily habits.  And if every member of your species lived with that same fear, there would be places no one in their right mind would go and choices between death by starvation and possible death by being eaten.  After all, fish are always eating other fish.  Let’s take a journey through the low end of the food web and see what horror can teach us about marine ecology.

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