The frequent criticism of Burroughs Barsoom is that it makes no ecological sense.   On Earth, the predator prey ratios are fairly consistent, with one lion to one hundred gazelles or something like that.   Yet on Barsoom, John Carter seems to encounter nothing but predators.   Every time he turns around he has to fight a Banth, a White Ape or an Ulsio or some other monsters.   What the hell are these predators eating, there's no prey.   For the world to make sense, John Carter would have to be struggling knee deep in Thoat droppings.

Actually, this comes about from a fundamental misunderstanding of the Martian ecology, and a misapprehension of what is really going on.

One of the critical things we have to understand about the Martian ecology of John Carter's time is that it has clearly undergone a catastrophic mass extinction.

This is not a wild guess.  Take a look at the remaining species:   The ten-legged dinosaur-sized Zitidars, the eight-legged thoats, the banths, calots, white apes, soraks, etc.   These are all highly evolved and fairly distinctive creatures.  They inevitably came from an extensive evolutionary line, actually, from several individual lines,  and evolutionary lines frequently branch.

If we look at Earth, for example, we do not have only one species of hoofed animal, but hundreds.   A creature like a Moose has a range of cousins ranging from close relatives like deer, antelope, cattle, bison, sheep and goats, to more distant hoofed relatives like rhinoceri and elephants.   We do not have only one or two species of predator, but rather, cats differentiate into Lions, Tigers, Cheetahs, Pumas, Leopards and Panthers, canines differentiate into dogs, wild dogs of different sorts, wolves, coyotes and foxes.  Even rodents differentiate to everything from squirrels to beavers.   Only comparatively rarely does an evolutionary line wind up with a single representative, like horses or elephants, and in those cases, it is apparent from fossil records that related species existed but were pruned away.

But on Barsoom, we appear to have nothing but single evolutionary lines.   This is hardly plausible.   We might expect one or two in a diverse fauna, but hardly single representative after single representative.    The closest we get to indications of related species is with the Green Man and the White Ape, who are clearly distinct but closely related species.   More distantly, Soraks and Apts are also six-limbed creatures like the Green Man and White Ape.   But the gulf between Soraks, Apts and their cousins suggest a far richer evolutionary lineage than the current representatives suggest.  Where are these other species?

The Banth, an ‘eight-legged’ Barsoomian lion, on the basis of the number of limbs, seems to be distantly related to the Thoat.  Again, this suggests a well developed and rich evolutionary lineage where predator and herbivore parted ways and evolved into quite different creatures.   But this evolution should have produced more varieties of each.  Where are they?

Obviously, they're all dead Jim.   Most of the hypothetical additional creatures off the six legged, and the two eight legged lines of evolution are no longer around.  They are extinct.   The implication is that the majority of species of Barsoom are now extinct.

The same likely holds true for plant species.   A world with oceans and abundant waters produces a massive profusion of plant life occupying a massive array of ecological niches.   With the desertification of the planet, most of those niches are gone.

At an estimate, somewhere between 75% and 80% of all the land species, plant and animal, that were extant prior to the droughts and desiccation of the seas are now extinct. 

Most of the planet's remaining biodiversity is to be found in remnant ‘island ecologies.’  The two big ones are the Valley Dor and the Toonolian Marshes.   There are smaller pockets of biodiversity remaining in the Kaolian Forest, the Invak Forest, the salt Marshes of Gathol, Bantoom, Kamtol, Ghasta and a few other small possible pockets.

These ‘islands’ doubtless contain specialized species that were particular to those regions all along.  But there is also evidence that these areas are the last refuges for species which were previously widely distributed.   Consider the case of the Malagor, whose range formerly extended over a substantial territory, but was believed extinct until a small population was rediscovered in the Toonolian marshes.

However, the extent of the devastation can be appreciated in the fact that these areas make up less than 10% of the planet's surface area.   It is likely that they make up less than 5% of the surface area.   If we take these small isolated areas out of the equation, the extent of species depletion and biodiversity loss in the rest of Barsoom is probably up around 99%.

With respect to sea and ocean species, the level of extinction is definitely at or near 99%.   Only in Korus and Omean would diminished sea populations survive in any or numbers diversity.   Some species of fish fish were noted in the Ghasta region, and likely exist in the Toonolian marshes and other areas.  But at the same time, red men in Ghasta were completely unfamiliar with fish, which in turn suggests that there are no significant fish populations in canals or rivers.   The the polar ocean, and the Hellas basin fish and sea life populations must be deemed to be entirely extinct.

And this leaves us with what?    Not, unfortunately, the Barsoomian equivalent of Giraffes and Birds of Paradise.   The most specialized creatures have all died off.   All but the hardiest creatures, adapted for the most marginal climates have died off.   We are left with a species poor ecology.

But the survivors....  The survivors are tough.   And more than that, they're adaptable and not terribly specialized.    Earth is currently undergoing a mass extinction, and its entirely possible that we might wind up doing for ourselves as well.  It is easy to imagine some future Earth being occupied by nothing but rats, rabbits, raccoons, crows, gulls and dogs.   These are the hardiest, most adaptable, most generalized and omnivorous species of Earth.

This then, represents the remnants of the martian ecology.  The toughest weed species on the planet, the most incorrigible pests and vermin and scavengers, the least discriminating of the omnivores.

And, most likely, they represent species previously adapted to harsh, arid desert conditions, and well equipped to survive in these situations.   Essentially, desert species have spread through the planet. 

So lets turn to the Banth.   The reality is that the Banth is not really the Barsoomian lion, though there may be some resemblance.   Nor is the Calot truly a Barsoomian dog.

What the Banth really is, is the Barsoomian Bear.   It is a powerful, voracious and skillful Martian omnivore.    The question is, what does a Banth eat when John Carter is not around?   The same thing that thoats eat.   The moss and the few remaining plants and shrubs that make up the Barsoomian botany.   The Banth eats meat of course, any meat it can catch or kill.   But most of its diet is the vegetation.   And of course, Banths, as large herbivore/omnivores in a very poor environment, are extremely territorial.   The greenery isn't enough to support competing herbivores as well, so the Banth is highly motivated to eliminate the competition, who become fine dining.

The real role of the Banth in the relic Martian ecology is a highly territorial and aggressive apex herbivore which kills and eats rival herbivores.   It may even prefer meat, but basically, it eats what it has before it.

By the same token, the Calots are a smaller, but equally generalized omnivore/scavenger.   More sociable and adaptable than the Banth, as well as highly intelligent, they have found a degree of toleration and acceptance at the fringes of Green and Red Martian societies.

The Great White Apes, of course, are another adaptable and intelligent omnivore/scavenger, who have found viable habitats in dead cities and badlands.

Meanwhile, the Ulsio is probably the most generalized of all, not just an omnivorous carnivore/herbivore, but likely an insectivore, a carrion and offal eater, and a wood gnawer.   Widely distributed, this tunneling creature is closest to the terrestrial rat.

Creatures such as Thoats and Zitidars, in contrast, seem to exist only in the context of Red Man or Green Man habitation.   While it is likely that there are wild populations, most of the species are domesticated animals.   The reality is that the Thoat and Zitidar are not sufficiently well adapted to much of the harsh Barsoomian environment to survive without the help of intelligent species.   The Banths and Calots, the true dominant herbivores would out compete them, and as predators, would simply hunt them down.

Apart from the Banths and Calots, and the intelligent species with their companion animals, the bulk of the Martian ecology is almost bare.   We have likely only a handful of small common species.

There are, of course, ecological islands, possibly a number of them of varying sizes, which preserve plant and animal species, but these species are relentlessly confined to their ‘island’ habitats.   However, the odds are that these ecological ‘islands’ are not particularly stable.  They are isolated not by oceans and seas, but by desert and subsistence level lands, which mean that the surviving ‘catastrophe’ species, for the most part, have access to them.  Of even more concern, the stable conditions in these islands are the product of geological and meteorological flukes.   Flukes can change without substantial notice.    Further, most of them are too small to be truly self sustaining over any long period.   The likelihood is that most of the smaller ‘islands’ have experienced and will continue to experience simplification.  The most vulnerable species will continue to disappear from these areas.   The insectlike Sith, formerly an apex predator in the Kaolian forest is considered to be near extinction.

It is a disturbing fact that many of the ‘islands’, including some as large as Omean and Dor/Korus, as well as smaller and medium sized regions like Kamtol, Ghasta, Bantoom, etc., appear to have survived simply because they were largely unknown to their neighbors and the Barsoomian population in general.

All of this indicates that while Mass Extinction has stabilized in most of Barsoom, it is likely to continue within the ‘island’ zones.

Because the source of Barsoom's extinction event appears to be massive climactic change and environmental desiccation, it seems unlikely that these factors will change.  For better or worse, Barsoom's current configuration, bereft of water with a borderline atmosphere, will either continue indefinitely or worsen.

Thus, the likelihood is that life will continue to subsist at low densities on Barsoom, with an increasingly simplified ecology of increasingly hardier desert-adapted species.

Mars Art by Joe Jusko