As humans change the world, predators seize the chance to succeed



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A boobook enjoys its vantage point, courtesy of humans.
Simon Cherriman, Author provided

Bill Bateman, Curtin University and Trish Fleming, Murdoch University

If you have ever been to a nature reserve in Africa, you may have been lucky enough to see predators on a kill – maybe something spectacular like lions on a giraffe. The chances are you got to see that because the predators killed the prey right on the road, where you could get up close in your car or safari vehicle.

Lions gathered on a road in a South African National Park.
Bill Bateman

But what if this was not just luck? What if lions had greater hunting success along a road because their prey slip on the tarmac, stumble and fall, thus becoming a meal? The road – a human intrusion in a natural world – could be increasing the predators’ hunting success.

Road kill.

This intriguing idea led us to wonder if there were other examples in which human structures or environments might benefit predators – a group of animals that would otherwise appear to want as little to do with humans and their world as possible.




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Ecosystems are dynamic, which means that new ones can arise when species occur in combinations and numbers that have not happened before. While we often (rightly) have a very negative view of our impact on the natural world, sometimes organisms can surprise us by taking advantage of what we do and creating a successful space for themselves in a human world.

Once we started looking, we found other examples of predators exploiting these niches. We found four ways, with much overlap, that predators take advantage of human habitats to improve their hunting success.

A world of opportunities.

First, certain animal species follow human settlements and can provide a completely new food source for predators. Rodents (rats and mice) and invasive birds (such as sparrows or starlings) exploit resources around towns. Pets and livestock are also commonly taken by predators such as bears, wolves, foxes and dingoes.

Lions have learned to use cowbells to locate livestock, and may have increased hunting success using gravel and tarmac roads to chase prey.
Trish Fleming

Second, potential prey species often gather around artificial resources, reducing commute times for predators and increasing their hunting success. For example, European kestrels ambush populations of bats and swifts as they leave their roosts in building ventilation. Two species of sea lion have learned to travel 100km up the Columbia River in the United States to hunt masses of migrating salmon that gather at fish ladders (structures that help fish go over or around dams or other barriers when migrating upriver to spawn) over the Bonneville Dam. Brown bears, meanwhile, hunt at fish weirs, trapping congregations of fish against these to prevent their escape.

Third, structures we build or things we do can make prey species more vulnerable. African wild dogs take down larger prey when they chase them into fences, and dingoes exploit roadkill along major highways. Horse-eye jack fish ambush prey around dock pilings that interrupt the synchronised escape behaviour of the fish schools. Peregrine falcons in New York city hunt at night as they have more success catching pigeons that are bedazzled by skyscraper lights. Lions have learned to use cowbells to locate livestock. Here in Australia wedge-tailed eagles follow harvesters on farms to catch animals flushed out by the machinery.

Finally, some predators also use resources that we provide as tools to aid their hunting. Some birds use human refuse to lure fish to their doom and many raptors use lampposts and aerials as perches, increasing their hunting success. Larger species such as cheetah and leopards similarly exploit our presence to hunt more successfully.

Osprey on aerial.

Only a few studies have tried to quantify the benefits of human environments for predators, identifying how they experience increased hunting success, reduced energy expenditure, or increased reproductive output. Such benefits can ultimately lead to increased population sizes, as has happened with the New York kestrel population and Chicago’s coyotes.

We predict that some predators are likely to become more abundant in our lives, which could have both positive and negative implications. For example, they are important biocontrol agents and do a great job of suppressing rodent populations. However, interactions with large predators can be dangerous for humans.

Letting humans do the hard work.

Predators can be vital for maintaining a balanced ecosystem. However, predator species can have a huge effect on their environment, even when there are only a few of them about. Predator species can easily become invasive animals, as we have seen with the introduction of cats into Australia or brown tree snakes onto the island of Guam.




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These predators have had devastating consequences for whole ecosystems, and our actions may be unwittingly increasing their advantages over prey species, as has been made evident by ravens using human-built perches to predate heavily on desert tortoises. Similarly, animals using road underpasses are more vulnerable to introduced red foxes as the foxes – clever animals – soon learn to wait at the underpass exit for a meal delivery.

The ConversationOur presence and the way we alter our environment can therefore thwart conservation of threatened species, despite our best attempts. We need to carefully consider how we influence our environment, and be on the lookout for instances where predators are making use of novel niches to exploit prey species. Even the smallest changes we make can affect a whole landscape, and can make prey animals more vulnerable.

Bill Bateman, Senior Lecturer, Curtin University and Trish Fleming, Associate Professor, Murdoch University

This article was originally published on The Conversation. Read the original article.

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Coal closures give South Australia the chance to go 100% renewable


Mark Diesendorf, UNSW Australia

South Australia is facing the closure of its Northern and Playford B power stations and Leigh Creek coal mine, after Alinta Energy yesterday announced plans to shut them ahead of schedule. It will cost 438 jobs in the coal-mining and coal-fired electricity industries. But this threat to employment could be transformed into an opportunity for creating many new jobs in renewable energy.

The South Australian electricity system could be operated entirely on scaled-up, commercially available, renewable energy sources. This is the conclusion of my forthcoming report (to be published next week) to the Conservation Council of South Australia.

Our modelling at UNSW Australia shows that the SA system could be supplied mainly by a mix of wind power; solar photovoltaic (PV) panels, both on rooftops and in large solar farms; and concentrated solar thermal (CST) power with thermal storage. Gas-fired turbines and demand management via “smart” meters and switches would manage the infrequent small lulls in wind and solar supply.

I estimate this transition would take 15–25 years, during which time the natural gas fuel for the gas turbines would be gradually replaced by biofuels from agricultural residues – thus making the system fully renewable. There would be increased trading of electricity with Victoria and possibly over a new transmission link to New South Wales.

Already a leader… by Australian standards

SA is already the leading Australian state in non-hydro renewable energy, with about 40% of annual electricity consumption now coming from wind and sunshine. SA has already shown that it can operate reliably and stably for hours when the contribution of variable renewable energy reaches two-thirds of demand, and last weekend wind power and gas coped admirably when the coal-fired Northern power station went unexpectedly offline.

In Europe, the idea of a state moving to 100% renewable energy would not be regarded as a controversial proposal. The north German states of Mecklenburg-Vorpommern and Schleswig-Holstein are already operating on 100% net renewable energy, mostly from wind. The “net” indicates trading with each other and their neighbours. Although SA has transmission connections to Victoria only, it has the advantage over northern Europe that it is very sunny as well as windy.

Bye bye baseload

Our calculations show that SA does not need any baseload power stations, such as coal or nuclear. Indeed, the lack of operational flexibility of coal and nuclear makes them poor partners for high penetrations of variable renewable energy. The SA system has already operated reliably for long periods without its coal-fired stations, as last weekend’s incident demonstrated.

Moving fully to renewable energy will deliver environmental, social and economic benefits. The transition would reduce SA’s greenhouse gas emissions, air pollution and associated respiratory diseases. It would cap electricity prices.

SA could create a wide range of new jobs in manufacturing, installation, grid connection, technical support and sales, which could help to compensate for the forthcoming job losses in its coal industry.

As for the nuclear question, the multinational financial analyst Lazard estimates the average costs of subsidized new nuclear energy in the United States in 2017 to be 12.4–13.2 US cents per kilowatt hour (kWh), compared with unsubsidized costs of 3.7–8.1 c/kWh for onshore wind, and 7.2–8.6 c/kWh for large-scale solar PV. For Britain’s proposed new nuclear power station Hinkley C, the UK government is offering a guaranteed price of 9.25 p/kWh (14 US c/kWh) increasing with inflation for 35 years. Thus new nuclear energy prices are roughly double those of onshore wind, and also higher than those for solar farms.

Compared with nuclear power, an appropriate mix of renewable energy sources is just as reliable, less dangerous, cheaper, emits less carbon dioxide overall, offers a wider range of environmental, health and employment benefits, can be implemented much more rapidly, and is more likely to enjoy community support.

What’s more, a nuclear power station (600 megawatts or more) would be too big for the SA grid system, and smaller “modular” reactor designs are not yet commercially available. Renewable energy, in contrast, is technically and economically feasible, and environmentally and socially desirable.

The Conversation

Mark Diesendorf is Associate Professor and Deputy Director, Institute of Environmental Studies, UNSW at UNSW Australia.

This article was originally published on The Conversation.
Read the original article.