Large Ecosystem Functions and the Effects of Extinction

Angela Harvey IBD 4 Final Review Paper

Abstract

Large herbivores represent some of the most iconic animals on the planet. These creatures are frequently keystone species as well as flagship species for their environments.

Unfortunately, many of them are in danger of extinction in those same habitats. The biomes and ecoregions large grazers and browsers inhabit cover six of the continents, and include grasslands, forests, and shrublan ds. Since many large grazers are keystone species, the services they provide are critical to the health of the ecosystem. The loss of these mammals through extinction would have cascading effects on the areas they inhabit. One order of large herbivores, th e

Perissodactyla, are uniquely situated to illustrate herbivory and its function. Since most of the large herbivores are grazers, at least part of the time, grassland ecosystems are used as case studies to highlight the services provided. For background on extinction and its consequences, historical studies of the Pleistocene - Holocene transition are investigated.

Introduction

Large herbivores represent some of the most iconic animals on the planet, such as the

African ( Loxodonta africana ) and the white ( Ceratotherium simum) . These creatures are frequently keystone species as well as flagship species for their environments

(Howland et al., 2014; Blair, Nippert, & Briggs, 2014). Unfortunately, many of them are in danger of extinction in t hose same habitats. Approximately 60% of the 74 largest land herbivores

are listed as threatened, including all 10 of the largest of Hippopotamidae, Elephantidae,

Hominidae, and Tapiridae families as well as 15 of the 20 species of the Suidae, Equidae,

Rhi nocerotidae, and Camelidae families (Ripple et al., 2015). Today, there are eight

species (weighing over 1000 kg), a significantly lower number than were present in the late

Pleistocene (~42). Seven of these eight are threatened and four are crit ically endangered, with the

only species showing improvement being the southern white rhinoceros ( C. simum ) (Ripple et al., 2015), which has increased from fewer than 100 individuals at the turn of the last century to approximately 20,000 today after an i ntensive effort to save the species. The recent increase in

poaching may yet place the white rhinoceros ( C. simum ) in company with its other megafauna

cousins, though. (Cromsigt & Te Beest, 2014; Sodhi, Brook, & Bradshaw, 2009; Weigl &

Knowles, 2014). In a ddition, the ranges of the 74 species of large herbivores is shrinking. Of the

25 species that have had range contraction estimates, they are currently, on average, occupying

only 19% of their historical ranges (See Fig. 1) (Ripple et al., 2015).

Fig. 1 - “Range contractions over time for three iconic African herbivores. African elephant. ( L. africana ), ca. 1600 versus 2008, common hippopotamus ( Hippopotamus amphibius ), ca. 1959 versus 2008, and black rhinoceros ( Diceros bicornis ), ca. 1700 versus 1987. The historical ranges are in blue, whereas the most recent ranges are represented by darker - colored polygons. For security purposes, the most recent black rhinoceros range polygons (1987) have been moved by random directions” (Ripple et al., 2015, p. 4)

T he biomes and ecoregions large grazers and browsers inhabit cover six of the seven continents, including tropical and subtropical moist broadleaf forest, grasslands, shrublands, savannas, mangroves, and other forest or grassy types (See Fig. 2, Ripple et a l., 2015). Since many large grazers are keystone species, the services they provide are critical to the health of the ecosystem. The loss of these mammals through extinction would have cascading effects on the areas they inhabit. Large herbivores shape the landscape through or browsing, trampling, wallowing, and other actions. They can affect other species directly and indirectly through the food web, and they modify abiotic processes by altering nutrient cycles, the properties of the soil, and fire regimes. There is an economic connection to humans, too, when the iconic species of a given territory attracts tourism, creating an economic web around the large herbivores and their environments. These processes cannot be assumed by small herbivores, thu s their ecosystem services are essential (Ripple et al., 2015; Blair et al., 2014; Austrheim, Speed, Martinsen,

Mulder, & Mysterud, 2014; Howland et al., 2014; Gill, 2015).

Fig. 2 - “Large total species richness (A) and threatened (B) at the ec oregion level. Ecoregion lists for each species were obtained using the IUCN Red List species range maps and are based on the ecoregions whe re each species is native and currently present”. (Ripple et al., 2015, p. 2)

In light of the fragile state of so m any large herbivores, a review of current literature is

necessary in understanding the role grazing and browsing plays on the health and diversity of

ecosystems and the welfare of the various species affected. Data from the fossil record of the

Pleistocene - Holocene transition gives good insight into the role large herbivores play in

ecosystem engineering and the possible effects of extinction (Cromsigt & Te Beest, 2014; Weigl

& Knowles, 2014; Bakker et al., 2016). Furthermore, since most large herbivores a re grazers or

mixed feeders (Shipley, 1999;Newman, 2000), an in - depth look at grasslands and related biomes, like steppes or savannas, clarifies the interactions of grazers and browsers with the other species of their environments. To highlight specific ec osystem services and the effects large herbivores have on their habitats, examples from the order Perissodactyla, the odd - toed ungulates, are considered. This order is highly relevant to the study of large herbivore extinction and diversity, since 13 of th e 16 species are endangered (with many extinct species represented in the fossil record), and they occur in ecosystems with a high level of biodiversity (Perissodactyl

Preservation Fund, 2016).

Megafauna in the Pleistocene

The unique relationship between large herbivores and their habitats is not a new concept.

The fossil evidence shows a long history of grazers and browsers maintaining a balance between

the various plant species and the needs of the animals living off of th ose plants. Several studies

have posited that large herbivores during the Pleistocene contributed to the vast amounts of open

land during that period (Cromsigt & Te Beest, 2014). One such article suggests that the meadows

in the Appalachian mountains were not cleared for human use in recent history but are artifacts

left over from the time of the megafauna (Weigl & Knowles, 2014). The authors argue that the

large herbivores that were abundant during the Pleistocene would have possessed the tolerance, mobili ty, strength, and diverse diets that permitted them to modify high - elevation habitats. They

also claim that this theory of megafauna engineering would apply to the debate over Europe’s

past. While some believe the continent was one unbroken forest, Weigl & Knowles (2014) cite

studies supporting evidence that Europe was more a mosaic of grasslands, forests, and transition

areas.

Bakker et al. (2016) combined present day studies with paleo - data to determine the

effects of megafauna on vegetation. The authors found several incidences that suggest large

herbivores altered the landscape to maintain open, grass - dominated habitats. Wear patterns on

teeth and tusks of mastodons ( Mammut americanum ) suggested bark - stripping behavior, which would have a marked effect o n woody plants. The reduction in tree cover and woody shrubs would then allow shade - intolerant plants, like grasses and forbs, to grow. Paleoecological

evidence of geomorphological engineering by mammoths ( Mammuthus primigenius ), like

digging, wallowing, o r trampling, would also have created open spaces for herbaceous

vegetation. There is evidence for this theory in the pollen records of the Pleistocene - Holocene

transition that show hardwoods increased immediately following the megafaunal decline.

Johnson ( 2009) argues that the rise in water tables, loss of soil fertility, and increase in

mosses in the mammoth steppes of North America and Europe during the Holocene was due to

the loss of the megafauna. There is evidence that suggests the transition from step pe to tundra

was due not just to climate change but to the lack of ecosystem engineering by the large

herbivores that populated the biome. Grasses allow higher rates of transpiration of soil moisture

than moss, and the cropping of the grass would have expo sed soil to rapid thawing and higher

temperatures in warmer months. Without the grazing pressures, water tables rose, creating a

favorable habitat for mosses, which insulate soil, keeping it cool and waterlogged. This, in turn, slowed the recycling of nutr ients, accumulating organic matter on the surface and reducing soil fertility. The author suggests that the engineering of the steppe by the megafauna may have damped the effects of climate warming on the vegetation, the effects of which were only truly fe lt after the disappearance of the engineers.

Using evidence from the fossil record, Faith (2012) makes a good argument for present - day conservation practices that may provide Africa’s Cape mountain zebra ( zebra zebra ) with better options in the futur e. With information gathered from historical data on megafauna in

South Africa, the author makes a case for expansion of the present - day reserves to include agricultural grasslands. He suggests that the nutrient - rich grasslands would provide a better envir onment for the zebra than the current areas dominated by fynbos, or heath - like, vegetation.

The Cape mountain zebra ( E. zebra zebra ) were present in large numbers during the Pleistocene in the area currently being used as conservation land, but the vegetat ion was more grass than heath. The shift from open grassland to fynbos vegetation that occurred at the beginning of the

Holocene correlated with a marked decline in zebra in that region. Faith (2012) cites this as evidence that the heath - like habitat is no t ideal for Cape mountain zebras and a more grass - dominated ecosystem would allow the populations to grow.

Grassland Ecology

Grasslands are regions that are dominated by grasses as well as sedges and forbs, but loosely defined, they may also encompass are as with sparse woody vegetation, in the form of shrubs and trees, or succulents, like at the edge of deserts. These may include tallgrass and shortgrass prairies, savannas, steppes, and mountain meadows or montane (Blair et al., 2014).

Grass - dominated ecos ystems frequently occur at the edge of forests and between forests and deserts (Baudena, et al., 2015; Weigl, & Knowles, 2014; Milchunas, Sala, & Lauenroth, 1988). Grasslands are limited by three main factors; climate, fire and grazing. Climate limitations are

mostly based on the availability of water, but extreme fluctuations in temperature is also a factor.

The variations in water availability give grasses and herbs dominance in most grass - type

ecosystems since they can survive on less soil water than tre es, although some types, like

savannas, are climatically suited to woody encroachment. In these cases, as well as the drier

grasslands, fire and herbivory play an important role in maintaining the dominance of the

grasses. (Blair et al., 2014; Milchunas et al., 1988; Baudena, et al., 2015; Weigl & Knowles,

2014).

Regions dominated by grasses and herbs contain a higher percentage of biomass growth

underground than above ground, giving a higher root - to - shoot ratio than forests. Grasslands also frequently ent er dormant periods, due to seasonal variations in water and temperature. This produces highly combustible standing shoots and ground detritus, making a perfect environment for fires (Blair et al., 2014). Most grasslands have evolved in such a way to take a dvantage of periodic fires. The fires are usually fast - moving, so the soil temperature does not rise high enough to damage the root systems. And the grasses and herbs make use of the increase in nutrients from ash and lack of shade to grow more quickly. Fi re also clears out any woody encroachment, giving the grasses and herbs an advantage (Blair et al., 2014; Baudena et al.,

2015).

Herbivory also maintains grassland ecosystems by altering the dynamics of the vegetation. Grazers reduce taller grasses and se dges, increasing light availability for the shorter herbs and grasses (Rueda, Rebollo, & Garcia - Salgado, 2013). Browsers reduce the amount of woody vegetation, allowing for the dominance of the grasses and graminoids (Baudena et al.,

2015). Consuming plant matter can also reduce the frequency and intensity of fires in grassy habitats by reducing the amount of combustibles at the surface (Weigl & Knowles, 2014).

Nutrients are made available for reuse in grasslands by herbivore digestion through urine and fec es, which is a form more quickly processed into the ecosystem than through normal leaf deposition and decay (Blair et al., 2014). Trampling, wallowing, and other behaviors alter the physical landscape, giving rise to small areas of altered species composit ion (Austrheim et al.,

2014).

Grasslands are important to the biodiversity of the planet for many reasons. Since grasses have a high root - to - shoot ratio, they sequester quite a bit of carbon underground. This keeps the soil high in nutrients and organic ma tter (Blair et al., 2014). Since grasslands occupy approximately 40% of the earth’s land surface (more than any other single biome), this carbon storing is critical to the present rise in greenhouse gasses. It has been estimated that grasslands store over 10% of terrestrial biomass carbon and almost 30% of the global soil organic carbon stock (Wang, VandenBygaart, & McConkey, 2014; Macdonald, et al., 2015). With fertile soil, diverse forage selection, and high nutrient content comes a vast amount of species that live in or near grasslands, with some of the highest biodiversity occurring in grass - type ecosystems

(Lorenzen, Heller, & Siegismund, 2012; Diacon - Bolli, Dalang, Holderegger,& Bürgi, 2012).

This fertility has also given given rise to agriculture and the raising of livestock throughout history as well as an excellent laboratory for ecosystem and conservation research (Blair et al.,

2014).

Large Herbivores and Grasslands

Large herbivores can have profound effects on ecosystems. As keystone species, the y help to maintain the open nature of their habitats and promote the survival of other organisms in the environment. Studies have shown that herbivores have been pivotal participants in the engineering of African savannas, English Downs, Dutch salt marshes , the Camargue of France, and the prairies of America (Weigl & Knowles, 2014). The body size of large herbivores gives more weight, practically and metaphorically, to the effects of foraging, landscape engineering, and nutrient cycling (Gill, 20 15; Howla nd et al., 2014).

Experiments on exclusions based on herbivore size showed that accounted for

80% of woody plant loss and when elephants were excluded, trees increased by 42%. Since most large herbivores will strip bark from woody plants and bro wse on saplings, the exclusion of large herbivores tends to increase the woody vegetation (Bakker et al., 2016). Open areas without tree cover support a number of plant species that are specifically suited to that environment, such as light - demanding herbs , shrubs, oaks (genus Quercus ), and hazels (genus Corylus ) (Johnson,

2009). The thinning of woody vegetation also benefits smaller vertebrates, like the angulate tortoise ( Chersina angulata ), giving them access to territory not available in dense forest (Kerley

& Landman, 2006; Ripple et al, 2015). Use of wallows and trampling, such as the sand wallows of American bison ( Bison bison ), also generate habitats for many specialist species of arthropods as well as creating ephemeral pools that support select s pecies of amphibians and birds (Fox,

Hugenholtz, Bender, & Gates, 2012; Hess, Hess, Hess, Paulan, & Hess, 2014; Ripple et al, ).

The varied feeding habits of many large herbivores generate patches of short and long grasses, creating a diverse habitat for i nvertebrates and smaller vertebrates (Ripple et al, ;

Naundrup & Svenning, 2015). A good example is the use of and to maintain grasslands in the Netherlands to provide feeding areas for graylag geese ( Anser anser ) who, in turn, alter nearby reed beds during molting season. This grazing of the reeds creates a mosaic of shallow water areas, further providing habitat for other species (Svenning et al., 2016). Large herbivores are also integral to seed dispersal in their environments. Forest ele phants (Loxodonta africana cyclotis ) in the Congo disperse approximately 345 large seeds per day from 96 species, and Indian rhinoceros (Rhinoceros unicornis ) relocate tree seeds from forest to grasslands (Ripple et al., 2015). The seeds ingested by l arge herbivores frequently germinate well, and the seedlings from ingested seeds grow faster than seedlings from seeds dispersed by other means (Polak, Gutterman, Hoffman, & Saltz, 2014).

Large herbivores influence the food web in ways other than plant pre dation, as well. By feeding on plant matter, keeping the grasslands open, large herbivores provide more opportunities for predators to find and take smaller prey, since the prey is easier to spot in open systems. They directly provide large amounts of biom ass for predators and scavengers, and many of the more massive predators prefer more massive prey. Larger carcasses also provide more nutrients to a wider selection of scavengers, since they are rarely consumed completely in one sitting. In addition, herbi vores provide food for blood - sucking insects, like the tsetse fly

( Glossina spp. ), and offer a wealth of parasites for insectivores, like the oxpecker ( Buphasus spp .), (Ripple et al., 2015).

Large herbivores affect the property of the soils in their ecosys tem, which can have cascading effects on the plant biomass. Defecation returns nutrients to the soil in patches of concentration that can last for years, with the patches shifting over time, diffusing nutrients across landscapes (Ripple et al., 2015). Thes e nutrients may stimulate plant growth and productivity (Austrheim et al., 2014).The feeding on plant matter also alters soil properties such as moisture content or temperature. Trampling and other physical activities alters the structure and permeability of soils. All of these activities change the composition and success - rate of different plant species, and may contribute to changes in bacterial or fungal communities (Hodel

et al., 2014).

The decrease in plant biomass on the surface of the soil through g razing or ecosystem

engineering reduces the fuel for fire, influencing the frequency and severity of fires. For

example, the interactions and relationship between white rhinoceros ( C. simum ) and

mesoherbivores in South Africa result in fewer large, intense fires. And after the rinderpest virus

( Morbillivirus rinderpest) was eradicated in the 1960s, Serengeti wildebeest ( Connochaetes

taurinus ) populations increased. The grazing pressure resulted in widespread reduction in fires

(Ripple et al., 2015).

Biodiversity and Large Herbivores

Large herbivores increase the species diversity of the flora in grasslands by trimming the dominant species, allowing other herbaceous growth a chance to grow (Rueda, Rebollo, &

Garcia - Salgado, 2013; Austrheim et al., 2014). It has been shown that white ( C.

simum ) increase grassland heterogeneity by establishing grazing lawns, patches of short grass

among longer grasses (Cromsigt & Beest, 2014). The physica l engineering of large herbivores,

like trampling or wallowing, contributes to ecosystem diversity by creating a patchwork of

disturbed areas, giving rise to variations in biota. By comparing bison to cattle, Gill (2016)

showed that bison create a patchwor k of grass and herb disturbance that increases biodiversity in

the area. With seed dispersal being one of the ecosystem services of large herbivores, they

contribute to the genetic diversity of a region by carrying genetic material long distances. This

gen e flow allows for genetic variation between populations (Ripple et al., 2015). A model on the

loss of as seed dispersers through over hunting in the Amazon showed large effects to tree populations and carbon storage that rivaled deforestation (Peres, Emilio, Schietti, Desmouliere,

& Levi, 2016).

The specific effects of large herbivores on their ecosystems seems to be determined by the productivity of the biome and the abundance and composition of herbivores (Blair et al.,

2014; Eby et al., 2014). For example, large herbivores can affect the health of arthropod communities in grasslands through unintentional ingestion, trampling, resource allocation for specialized groups (such as dung beetles from the Family Scarabaeidae ), and alteration of the herbac eous cover. Generally, taller grasses favor arthropod diversity, so overgrazing would have a negative effect. Yet, there are arthropod species that thrive on short vegetation and patches of bare dirt. It has been proposed that a patchwork of short and long grasses would benefit the diversity of arthropods in grassy landscapes. This would suggest that a density of large herbivores that is supported by the ecosystem’s productivity consisting of a diverse grouping that favor different plants for forage would b e the healthiest option for arthropods (van Klink, van der

Plas, van Noordwijk, WallisDeVries, & Olff, 2015). Zhu, Wang Guo, Liu, & Wang (2015) also found that the effects of grazing depended on the diversity of the plant and herbivore species in an ecosys tem. Higher biodiversity resulted in better conservation of arthropods.

At higher grazing concentrations, though, large herbivores can have negative effects on their habitats, reducing the plant matter to an unsustainable level or overgrazing a particular species, especially in ecosystems with no evolutionary history of grazing (de Villalobos & Zalba,

2010). This may have effects on other animals. Overgrazing causes a shortage of fodder for small mammals that compete for the same food, such as . This , in turn, affects the number of small - mammal predators, like snakes. Two studies found a negative relationship with the abundance of large herbivores and reptiles in grassy regions. While moderate grazing had a positive or no effect on and reptile abundance, as herbivore numbers increased, rodent and

reptile populations decreased (Howland et al., 2014; McCauley, Keesing, Young, Allan, &

Pringle, 2006).

With the grazing pressure on an ecosystem being of utmost importance in the effects of

large h erbivores on biodiversity, it follows that a balance between the herbivores and their large

predators is necessary. If moderate or light grazing can increase biodiversity, then large

herbivores can be integral to the maintenance of grassland biomes and spe cialist species. But

overgrazing is a concern. The healthiest ecosystem will have a balanced predator/prey ratio at all

levels of the food web, but in light of the complexity of such relationships, more research is

needed (Svenning et al., 2016; Grange et al., 2012).

Perissodactyls

Perissodactyla is the order containing the odd - toed ungulates. It consists of the equids,

the rhinoceroses, and the . These species are herbivores, and they range in size from 200 kg

to 3500 kg. They balance on one or three toes and share elongated skulls, mobile lips, and

hindgut to aid in digestion (Perissodactyl, 2016). Their unique structure gives them

good mobility and the ability to graze or browse on many different types of plant matter. The

hindgut ferme ntation allows for better processing of taller and more fibrous grasses than

and the mobile lips give good purchase on short or small plant parts (Arsenault &

Owen - Smith, 2011). As examples, the Perissodactyls are good case studies in specific ef fects of

large herbivores on the health and diversity in their environments.

The white rhinoceros ( C. simum ) in East Africa has the capacity to digest fibrous material and the wide mouth and lip - plucking technique used when grazing grants the rhino the abi lity to

crop very short grass. As mentioned in “Biodiversity” above, this allows the rhino ( C. simum ) to create grazing lawns in its habitat by clearing the taller vegetation, allowing less abundant

herbaceous plants to grow. These lawns provide high - quali ty forage for other grazers and increase the abundance of shorter plants (Cromsigt & Te Beest, 2014; Arsenault & Owen - Smith,

2011).

The ability of Perissodactyls to generalize in their feeding habits can help when the ecosystem undergoes change. In a study on the extinct Hundsheim rhinoceros ( Stephanorhinus hundsheimensis ), Kahlke and Kaiser (2010) found a large dietary variability using fossil material. Individuals from two different European sites were analyzed to determine dietary preferences. It wa s shown that the environments of the two sites were vastly different, but that the rhinoceros ( S. hundsheimensis ) could thrive on either grass or browse, making it very ecologically tolerant. Unfortunately for this species, it was pushed out of all its hom e ranges by new, better adapted species. It is believed that loss of habitat through competition caused its extinction.

While all large herbivores may affect their ecosystems in similar ways, the effects are species specific. Take the zebra, for example. T he plains zebra and Grevy’s zebra look very much alike, seem to have the same requirements for survival, and both eat mainly grass. This might, at first glance, suggest a strong competition between them. But a study on dietary preference showed that these two species were niche differentiated on 14 grass and forb species.

Ten of the plants were mainly eaten by Grevy’s zebra and five by plains zebra (Tillman & Borer,

2015). This is a good illustration that seeming competitors in a grassland ecosystem may act ually be very different in their forage preferences, and the success of these species requires a high biodiversity in forage choice. There is a good study on reintroduction of species to restore ecosystem function. It involves seed dispersal by the Asiatic wild ass ( Equus hemionus ). The ass was reintroduced to the Negev

Desert in Israel with other ungulate species. By examining the dung of the Arabian oryx ( Oryx leucoryx ), Asiatic wild ass ( Equus hemionus ) and dorcas gazelle ( Gazella dorcas ), the authors found that each ungulate dispersed different plant species with little overlap. This showed that the reintroduction of the ass was integral to ecosystem restoration, even in the presence of other large herbivores (Polak et al., 2014). In this case, the specialization of dietary habits works for the health of the habitat.

Some Perissodactyls are considered invasive species, especially if the population inhabits an area with no history of large herbivores. This can have deleterious effects on an ecosy stem.

Feral horses ( Equus ferus ) have the same ability to digest fibrous plant matter as other perissodactyls and are not selective about the parts of a plant they eat, as cattle are. This means they are well - adapted to grazing on a wide range of species a nd types of pasturage. This creates a problem in grasslands when the abundance of horses outweighs the carrying capacity of the ecosystem. Biodiversity tends to suffer under heavy grazing in areas that evolved under low grazing pressures. The plants that e volve under such circumstances usually have no defenses against predation (de Villalobos & Zalba, 2010).

Conclusions

As the numbers of large herbivores declines, it becomes increasingly important to understand their function in the regions they inhabit. T he ecosystem services provided by large grazers and browsers cannot be assumed by the smaller herbivores in their habitats, so stopping the downward trend becomes important to the health and welfare of the biomes and to the planet as a whole. Larger specie s do seem to be at greater risk of extinction, due to overexploitation, long gestation periods, smaller population sizes, vulnerability to environmental perturbations,

and the need for larger habitats (Sodhi et al., 2009). As habitat loss, climate change, hunting

pressure, and human encroachment increase, the populations of large herbivores decrease,

causing cascade effects across trophic levels (Ripple et al., 2015). As witnessed by the studies on

the Pleistocene - Holocene transition, the loss of the megafa una caused vast changes in the

environment. Extinction of the large herbivores of today could have similar effects on our

environment, causing further extinctions to species who rely on these species and the habitats

created by them.

The future do es show some promise. As evidenced by Faith’s (2012) study on the Cape mountain zebra ( E. zebra zebra ) and Ripple’s et al. (2015) report of the increase in the southern

white rhinoceros ( C. simum ), some preservation efforts are succeeding. And reintroducti on

projects, like the Asiatic wild ass ( E. hemionus ) to the Negev Desert, could be very useful in

restoring ecosystem health and function. Future research needs to be conducted on the

effectiveness of reintroductions as well as on the interactions among tr ophic levels in large

herbivore ecosystems. There is also a need for research on several of the declining species. Most

of the studies conducted to date have focussed on non - threatened species, game species in

wealthy countries, and species in developed co untries. Since the declining herbivores are mostly

in developing countries, poorer countries, and, of course, are threatened, this suggests a gap in

present scientific knowledge (Ripple et al., 2015). As evidenced by the white rhinoceros in

southern Africa and the Cape mountain zebra, concentrated effort can bring species back from the brink (Cromsigt & Te Beest, until 2014; Arsenault & Owen - Smith, 2011; Faith, 2012).

Appendix: Definitions

Abiotic - something that is physical, not biological or living Biom e - a large community of flora and fauna of similar habitat

Biota - the flora and fauna of an area

Browse - feeding on leaves and twigs

Ecoregion - a major ecosystem of distinctive geography with uniform climate

Ephemeral pool - vernal pool, temporary pools of water

Fauna - animal life of an ecosystem

Flagship species - iconic species that capture the public’s attention, used for conservation initiatives

Flora - plant life of an ecosystem

Forb - herbaceous flowering plants other than graminoids

Fynbos - heath - like vegetation in southern Africa with small heather - like trees and shrubs

Geomorphological - changes of the physical surface

Grass - herbaceous plant with long leaves, jointed stems, and wind - pollinated flowers

Graminoid - grasses, sedges, and rus hes

Graze - feeding on graminoids and forbs

Herbaceous - of or relating to seed - bearing plants without woody stems

Herbivores - animals that feed on plants

Heterogeneity - diversity, composed of different parts

Hindgut - the posterior part of the digestive system, the colon and its related parts

Holocene - second period of the Quaternary period that began approximately 11,700 years before 2000 AD

Keystone species - an important species in an ecosystem on which other species depend

Megafauna - large mammals, usually defined as weighing over 1000kg

Mesoherbivore - medium - sized herbivore, usually defined as weighing between 50kg and 500kg

Montane - mountain grasslands

Paleo - old, ancient, relating to the geological past

Pleistocene - the first epoch of the Qua ternary period, ended approximately 11,700 years before 2000 AD

Savanna - grassy plain in subtropical areas with scattered trees and shrubs Sedge - grass - like plant with triangular stems and inconspicuous flowers, grows in wet regions

Steppe - extensive, fl at, unforested grassland

Succulent - plant with thickened, fleshy parts that retain water

Trophic level - position an organism occupies in the food chain

Tundra - flat, treeless region of the Arctic with permanently frozen subsoil

Encyclopædia Britannica . Retrieved on April 19, 2016, from http://www.britannica.com/science/

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