Keystone species https://www.youtube.com/watch?v=_IWw8Ruz8Uo https://www.youtube.com/watch?v=JGcIp4YEKrc https://www.youtube.com/watch?v=hRGg5it5FMI As we all know this Earth we find ourselves on is fragile; all that we see in nature is just a series of delicately balanced interactions between species (including us). But sometimes certain species have a linchpin role in such balances. Keystone species are crucial species in an ecosystem. If they were to be removed from an ecosystem, there would a drastic impact on most of the species and the environment within that ecosystem. The term "keystone species" was coined by zoologist Robert T. Paine, and defines species which have a disproportionate effect on their environment relative to their abundance. Meaning they keep entire ecosystems in check, sometimes in very indirect ways. Fosa Photo Credit: Flickr | Rod Waddington The Fosa are impressive, odd looking animals endemic to Madagascar and, being the largest member of the carnivorous Eupleridae family, is in fact the apex predator of the island. Capable of hunting both on the ground and in the trees Fosa have an indiscriminate diet, preying on rodents, lemurs, snakes and even insects. Without the Fosa the populations of these animals would boom. Now, that may sound like a good thing to begin with, seeing as the majority of lemur species are endangered, however with nothing to keep them from overpopulating it would eventually lead to the overexploitation of their food resources. And with the increase in arboreal habitat loss through deforestation and fragmentation, competition for food would be exacerbated further. Snake and lizard numbers would also rise and the birds and small mammals they prey on would face the same overexploitation, causing the same eventual demise. These knock-on effects are referred to as cascade effects and are especially prominent in island ecosystems, even more so in endemic species food chains such as these. This is a very worrying notion as the forests that support all of these species are under threat, and has even forced the Fosa to depredate village chickens, leading to their persecution. Fosa numbers are low already, and given the fragility of endemic island ecosystems, further habitat loss could trigger these events. If you would like to help conserve these crucial habitats check out our Madagascar Conservation project. Tiger Sharks Photo Credit: Flickr | tobze Another example of the importance of apex predators is the Tiger Shark. Found in the Torrid Zone’s tropical oceans these sharks have a huge range, spanning the world's equatorial coastlines from Australia to The Americas and everywhere in between. It is because of this range, and their tendency to eat anything, that they are defined as an apex predator. In fact keystone species are more often than not the animals at the top of the food chain as they keep their prey populations healthy. By preying on the slowest, injured or weakest individuals, Tiger Sharks ensure only the fittest survive. They also directly ensure the vitality of sea grass beds by altering the behaviours of their prey. Left unchecked, sea turtles and Dugongs would intensively graze sea grass, overexploiting the resource. Yet with Tiger Sharks present the Dugongs and turtles are forced to move around or face predation, giving the sea grass chance to regenerate. Tiger Sharks have been persecuted for their shallow swimming habits and occasional human attacks, and have been hunted so much for their fins, meat and skins that they are currently declared as Near Threatened on the IUCN Red List. If you would like to see many species of shark whilst contributing to a better understanding of shark ecology, see our Fiji Shark Conservation project. Ochre Sea Star Pisaster ochraceus Photo Credit: Flickr | National Marine Sanctuaries This makes the top 5 because it was in fact the first species to be classed as Keystone. In 1966 Robert T. Paine had an idea that not all species have the equivalent impact on their environments. To prove this he began the gradual removal of an apex predator species from an ecosystem, in this case the Ochre Sea Star. This experiment was carried out over 3 years in Makah Bay on the coast of Washington State, and found that even with the removal of a few individuals the affects were considerable. Ochre Sea Stars feed on sea snails and barnacles but their main prey is mussels. These sea stars were so effective at keeping mussel populations down that when they were removed vast mussel beds established, overcrowding the rocky surfaces that limpets, barnacles, algae and sea snails depend on. This was the first documentation of Cascade Effects. Robert T. Paine's experiment was highly unorthodox and unethical by today's standards; however it did provide us with this invaluable knowledge, which is still used to define many other species’ vital roles in ecosystems. This discovery shifted the paradigm from ineffective species-specific conservation to management practises considering the overall protection of ecosystems. You can see these delicate ecosystems, and help to protect them on our Marine Conservation and Diving projects in Fiji and Belize. Grey Wolf Photo Credit: Flickr | U.S. Fish and Wildlife Service Headquarters So far we've seen what the absence of a single species could do to an ecosystem, but keystone species can also be used as a conservation tool. By considering the cascade effects of a lack of such species, logically the introduction of one into a niche would reverse these effects and benefit the ecosystem. In Yellowstone National Park, researchers discovered the park's Quaking Aspen tree population was in decline. Large, sprawling root systems make aspen one of the fastest growing and regenerating trees in the world, so this decline didn't make sense. The data showed aspens had been under duress for almost 70 years, with a severe lack of regeneration since the 1920s. It was found that the beginning of this decline coincided with the extirpation of Grey Wolves, wiped out by human hunting around 1926. With the lack of a niche predator Yellowstone's Elk population grew to be the largest in the world, and the park almost reached its Carrying Capacity; the ecological threshold between population size exceeding food resources, meaning that with the Elk over-browsing the new tree shoots, the aspens couldn't produce faster than they were being eaten. Grey Wolves were thankfully reintroduced in the mid 90's and changed a whole lot more than just Elk population. To avoid predation the remaining Elk were constantly moving around the park into less favourable habitats, ensuring the annual recovery of the forests. The Quaking Aspens naturally recovered, as did Yellowstone's willow trees, and with more willows came more Beaver colonies (a keystone species in its own right because of their effect on hydrological systems). Photo Credit: Flickr | AllAroundTheWest Wolves also preyed on Coyotes which led to the increase of rodents, and therefore smaller predators. Also bear, Raven and raptor populations also increased due to carrion leftover from wolf kills. This case demonstrates the level of interconnectedness in nature, because not only did the reintroduction of wolves benefit these species, but as the forests could mature and establish, there was less soil and riverbank erosion; actively changing the geography of Yellowstone. Bees Photo Credit: Flickr | Paul Rollings There are around 20,000 species of bee worldwide, spreading across every continent except Antarctica, and they fall into just 9 taxonomic families. As a collective they make one of the biggest keystone species in the world, responsible for a third of plant pollination worldwide, and over 70% of the crops we all eat. If bees were to disappear there would be a catastrophic cascade effect, more severe than any other single species. However this cascade would start from the bottom of the food chain. Without the necessary cross-pollination many wild and crop plants would die off and subsequently send ripples all the way up the food chain, similar to the overexploitation mechanics of Madagascar, but on a global scale. Some other species may be fine in the long run as "life finds a way", but our population is so dependent on their service that humans would face major consequences; huge reductions in food, textiles and even livestock farming to name a few. Photo Credit: Flickr | Archangel12 Bees are currently in decline all over the world, threatened by natural parasites, climate change and anthropogenic pressures such as habitat loss and the use of harmful pesticides. The parasitic varroa mites which attach to honeybees are a natural process, and would probably be an ecologically stable trade-off if it wasn't for the added pressure we pile on. The UK has seen an alarming 97% loss of its wildflower meadows, mostly due to making way for arable farmland. The irony being that we then spray these crops with harmful pesticides, such as neonicotinoids, that directly link to Colony Collapse Disorder (CCD). Thankfully neonicotinoids have been banned almost worldwide but they are still sometimes used for "emergency" pest situations in the UK. The advocacy of such substances and continued unsustainable land use is most likely to set these cascades into effect unless we do something. Elephants Elephants are among the most intelligent of the creatures with whom we share the planet, with complex consciousnesses that are capable of strong emotions. Across Africa they have inspired respect from the people that share the landscape with them, giving them a strong cultural significance. As icons of the continent elephants are tourism magnets, attracting funding that helps protect wilderness areas. They are also keystone species, playing an important role in maintaining the biodiversity of the ecosystems in which they live. During the dry season, elephants use their tusks to dig for water. This not only allows the elephants to survive in dry environments and when droughts strike, but also provides water for other animals that share harsh habitats. When forest elephants eat, they create gaps in the vegetation. These gaps allow new plants to grow and create pathways for other smaller animals to use. They are also one of the major ways in which trees disperse their seeds; some species rely entirely upon elephants for seed dispersal. On the savannahs, elephants feeding on tree sprouts and shrubs help to keep the plains open and able to support the plains game that inhabit these ecosystems. Wherever they live, elephants leave dung that is full of seeds from the many plants they eat. When this dung is deposited the seeds are sown and grow into new grasses, bushes and trees, boosting the health of the savannah ecosystem. There are hundreds of different species that depend on elephants for their survival. If elephants go extinct – so do they. In the 1950’s wildlife conservationist David Sheldrick was given the daunting task of transforming Tsavo East National Park in Kenya into a tourist retreat. However, he soon realized that illegal poaching was rampant. The few animals that were left were either too scared or too shy to make themselves known. How could he possibly make a tourist destination if there were no animals? Elephants were reintroduced back into the park and to his surprise…hordes of other animals soon followed. It wasn’t long before the once barren scrubland was transformed into a grassland oasis that became home to hundreds of animal species. David was one of the first to question the important role the African Elephant played in the habitat that surrounded them. Elephants can turn a barren scrubland into a grassland oasis Elephants tear down trees and drastically change the environment they live in. Initially this became a great concern to scientists watching the park go through a dramatic transformation. Instead of killing them, as had been proposed, David fought to keep them alive and instead simply observe. He felt there was more at play than what any of them could see. Greater Kudu As elephants tore down the trees David noticed that African wild grass began to grow where trees once stood. Seeds inside elephant dung served not only as a nutritious food source for smaller animals but whatever didn’t get consumed sprouted into new vegetation. An assortment of medium-sized plant species sprung up for animals that weren’t able to reach into the tops of trees such as the Greater Kudu. An elephant pushing down a tree The Balanite tree (Balanites aegyptiaca) is considered a very valuable resource in Africa. This native tree is solely dependent on elephants for the dispersal of its seeds through elephant dung. Many parts of this tree are used as famine foods in Africa and the wood is one of the primary sources of charcoal; a heat source for many homes. Elephants are not just the bulldozers of society but they are the gardeners as well. David was amazed at how many animals began to flourish in Tsavo after the elephants had returned. The elephants had merely transformed the landscape…not destroyed it. Today Tsavo East National Park is considered one of the most beautiful tourist safari destinations in the world. With safari tourism as the backbone of Kenya’s entire economy it doesn’t take much to think what would happen if elephants went extinct. Sea Otter The sea otter (shown below) is considered a keystone species as their consumption of sea urchins, preventing the destruction of kelp forests caused by the sea urchin population. Kelp forests are a critical habitat for many species in nearshore ecosystems. In the absence of sea otters, sea urchins feed on the nearshore kelp forests, thereby disrupting these nearshore ecosystems. However, when sea otters are present, their consumption of sea urchins restricts the sea urchin population to smaller organisms confined to protective crevices. Thus, the sea otter protects the kelp forests by reducing the local sea urchin population. Sea otters are an iconic species, representing the beauty and diversity of marine life found along California’s coastline. They’re also considered a keystone species because of their critical importance to the health and stability of the nearshore marine ecosystem. They eat sea urchins and other invertebrates that graze on giant kelp. Without sea otters, these grazing animals can destroy kelp forests and consequently the wide diversity of animals that depend upon kelp habitat for survival. Additionally, kelp forests protect coastlines from storm surge and absorb vast amounts of harmful carbon dioxide from the atmosphere. Sea otters are also considered a sentinel species because their health reflects that of California’s coastal waters.