Dispatches

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Using weather radar to track songbird migrations

Lindsay N Deel

Scientists and birders have long struggled to observe the elusive nighttime migrations of songbirds, but an innovative approach (IEEE Geosci Remote S 2015; doi:10.1109/TGRS.2015.2443131) developed by doctoral students at the University of Oklahoma (Norman, OK) relies on weather radar to detect the behaviors of these birds in the Great Plains of the US. Most songbirds migrate at night and often fly at heights that are very difficult to detect visually from the ground. According to author Kyle Horton, “To begin to understand how a migrant bird moves from one destination to another, you generally need two different measurements: track and orientation”. Track is calculated from wind characteristics (speed and direction) and the bird's velocity, whereas orientation is the compass direction in which the bird aligns itself. “You can think of track in terms of swimming across a river. You want to go straight across, but the current of the river causes you to drift downstream; this resultant direction is the track”, explains Horton. “Track is easily measured for most aerial organisms using radar techniques; however, orientation is much harder [to gauge].”

Figure 1.

Weather radar can track migratory songbirds like the Wilson's warbler (Cardellina pusilla).

Horton, a biologist, and lead author Phillip Stepanian, a meteorology and electrical engineering student, used the US weather surveillance system (Next-Generation Radar or NEXRAD) to examine –for the first time – track and orientation independently and at frequent intervals. The method allows researchers to determine how migrant birds cope with unfavorable wind patterns and how avian behavior changes over space and time. The approach has the added benefit of providing fine-scale measurements of bird migrations that occur over very broad scales.

Horton and Stepanian are already exploring different ways to apply NEXRAD to investigate other biological phenomena. This has been a big challenge, given that the system was originally designed to remotely monitor precipitation and wind patterns. “Our technique is just one method to extract orientation measures of migrants aloft, and I see no reason to think that this method won't be improved upon”, says Horton. “As we learn more about the data products, we'll begin to better understand what is working and what isn't.”

Dissipating plastic “smog”

Jen Fela

Plastic pollution in the ocean is less like an island and more like smog, according to Marcus Eriksen, Research Director and Co-Founder of 5 Gyres (Santa Monica, CA). “In the 1970s, the environmental movement used the term ‘smog’ to describe trillions of particles of carbon polluting our skies, swirling with atmospheric currents, and slowly settling to the ground”, says Eriksen. “Plastic smog in our oceans is [equivalent to trillions of hydrocarbon particles] swirling around the sea by ocean currents and slowly settling on the seafloor.” Eriksen and his colleagues estimate there are 5.25 trillion pieces of plastic in the sea, 92% of which are “microplastics”, pieces smaller than a grain of rice (PLoS ONE 2014; doi:10.1371/journal.pone.0111913). “We've found microplastics in all oceans, on all beaches, on the seafloor, within ice cores, and throughout the water column. The only smart solution is to stop the source”, he continues.

One source could be as close as the nearest pharmacy. In an earlier study on microplastics in North America's Great Lakes, Eriksen et al. discovered that many of the particles were similar in size, shape, and composition to the microbeads present in some major-brand personal care products (Mar Pollut Bull 2013; doi:10.1016/j.marpolbul.2013.10.007).

Environmentalists are increasingly worried that microbeads from these products are ending up in the world's oceans, claiming that the particles adsorb toxins and are ingested by marine organisms that mistake them for plankton (including fish eggs), and that they will eventually find their way into fish consumed by humans.

Industry representatives contend that there isn't enough evidence to indicate that microbeads from personal care products are a major source of microplastic pollution or that the particles pose a risk to the marine environment, but say they are supportive of companies' efforts to phase out the microbeads. According to Iain Davies, Senior Environmental Scientist for the Personal Care Products Council (PCPC; Washington, DC), “The various sources of plastic microbeads in the waterways have not yet been fully determined by reliable science; however, the personal care products industry is actively innovating to develop greener, biodegradable alternatives.”

Eriksen argues that the PCPC is supporting industry-friendly legislation that would allow plastic microbeads to be replaced with a biopolymer that does not degrade in the ocean and therefore does not solve the problem. Both sides declare support for a national ban on plastic microbeads, but whether such a ban would help to eliminate the smog may depend on the details of the legislation.

Catalyst protects fish from pharma feminization

Katherine Blackwood

Oral contraception is polluting our rivers – giving male fish female characteristics and threatening stock survival – but an innovation on the horizon may improve how we remove environmentally harmful chemicals from wastewater.

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are not effectively removed by conventional wastewater treatment plants. And while advanced treatment processes involving ozone or activated carbon may reduce micropollutant concentrations, the high costs and energy requirements of these systems preclude them from widespread use. According to Terry Collins (Carnegie Mellon University; Pittsburgh, PA) and Susan Jobling (Brunel University; London, UK), the senior authors of a recent experimental study (Sci Reports 2015; doi:10.1038/srep10511), an affordable and sustainable solution could be the application of chemical catalysts known as tetra-amido macro-cyclic ligand or “TAML” activators.

These activators are synthesized mimics of the peroxidase enzyme, which safely breaks down several pharmaceuticals, including 17α-ethinyl-estradiol (EE2), a synthetic estrogen in birth control pills. EE2 is persistent in freshwater ecosystems, and can cause egg cells to form in the testes of male fish, among other effects. “TAML acts on the estrogen in the water”, explains Jobling, “reducing its concentration so that the effects on fish are reduced or obliterated altogether”.

In addition to testing the efficacy of TAML on wastewater effluent, the researchers demonstrated that TAML effectively treats synthetic urine spiked with EE2. Pharmaceuticals are mostly excreted via urine. “If one could somehow remove pharmaceuticals from the urine in household wastewater upstream of the sewage treatment works”, continues Jobling, “one would reduce their eventual entry into surface waters and mitigate their ecological effects. This type of innovation would also support a paradigm shift in the ownership of waste-water treatment to incorporate a degree of self-management of waste-water by households, such that public awareness of, and responsibility for, water pollution would be enhanced”. Separating residential waste for recycling has come a long way in the past 20 years, and Jobling believes that similar shifts in attitudes and behavior should be possible for household wastewater.

However, a downstream approach is the team's next step; they hope to directly compare the efficiency and costs of the TAML process with that of ozone and activated carbon treatments by retrofitting TAML treatment into sewage treatment plants alongside its more expensive cousins. Jobling estimates that the TAML facilities will have 3–5 times lower operating costs and 5–10 times lower capital costs, while requiring 2–3 times less energy.

Honeybee-free pollination

Virginia Gewin

Early signs from the Cornell University (Ithaca, NY) apple orchard indicate that a commercial-level crop yield may be achieved through pollination primarily from wild native bee species. Most commercial orchards rely on non-native European honeybees (Apis mellifera) from rented hives to pollinate their crops. But honeybee hive managers have faced devastating declines in recent years, leaving apple growers in New York State with two options: pay higher hive rental costs or cut honeybee usage.

In 2008, Bryan Danforth, a bee biologist at Cornell, set out to learn more about wild bees' effectiveness in apple orchards. He and his colleagues have so far surveyed about 30 commercial orchards; the team found 105 wild bee species in the 13 000 samples taken. “In terms of pollinator diversity, these are rich agricultural systems”, says Danforth. To determine whether wild bees alone could maintain apple yields, Cornell's orchard staff took a bold step last year: they didn't rent honeybees. According to Danforth, “It was largely a proof-of-principle experiment”. If the Cornell orchard could maintain yields without importing honeybees, maybe others would reconsider their management practices as well.

Figure 2.

Wild native bees can be effective pollinators in commercial orchards.

The apple harvest won't occur until this fall, so it's too early to compare yield data to that from previous years when honeybees were brought in –but the yield looks promising. “My best guess is that we have a 100% full, normal crop this year with the wild bees as pollinators”, predicts Cornell orchard manager Eric Shatt.

Danforth and colleagues conducted surveys in recent years and found that roughly one-half of apple growers in the area use rented honeybees, which prompted their efforts to better document the pollination capacity of wild bees. “Big operations are more likely to rent honeybees, which is necessary because wild bees aren't as effective in heavily-managed orchards”, explains Danforth.

The Northeast Pollinator Partnership (www.northeastpollinatorpartnership.org), Danforth's new endeavor to help growers assess their potential for wild bee pollination, grew out of those surveys. The goal is to create a smartphone application and website to share data and data-collecting protocols, which will help guide growers' decisions about honeybee rental. “Growers are reconsidering this choice of whether to rent honeybees – it's a pretty dramatic change”, concludes Danforth.

100 safe passages for Asian elephants

Adrian Burton

A new coalition of conservation organizations, the Asian Elephant Alliance (AEA), was launched July 1st with the aim of conserving Asia's wild elephant (Elephas maximus) populations. Its main objective is to raise funds for securing migration corridors – narrow stretches of land along old migratory routes – that would allow elephants to move between fragments of suitable habitat across India. It's a mammoth organizational task but one that's already underway.

Only 35 000–45 000 Asian elephants remain in the wild, about half of which live in India. The AEA –formed by Elephant Family, the International Fund for Animal Welfare (IFAW), IUCN Netherlands, the Wildlife Trust of India (WTI), and the World Land Trust – hopes to stem further losses by raising US$31 million over the next 10 years to help secure some of the 100 migration corridors identified by IFAW and WTI. All lie within India's five major elephant distribution zones (in the southwest, along the border with Nepal, in two northeastern regions, and in Odisha and neighboring states).

Figure 3.

Longer, safer migrations may soon be possible for Asian elephants.

“The WTI has developed four models of securement [obtaining land for the corridors]”, explains Vivek Menon, the organization's executive director and CEO: “The Public Initiative model, urging governments to secure the land where acquisitions are not needed; the Government Acquisition model, assisting governments in acquiring land through official schemes for purchase and rehabilitation; the Private Purchase model, with WTI directly purchasing the land and relocating the people; and the Community Securement model, supporting community-based organizations to set aside land for securement.” Protection of the corridors from activities like logging and grazing is to be enforced by forest departments or village councils, as appropriate.

A handful of corridors have already been secured with AEA support. One corridor, which is in the process of securement and which connects the Kaziranga National Park and South Karbi Anglong Wildlife Sanctuary, involved the voluntary relocation of a village to a new site with better services, including utilities. The WTI insists there are no plans for mandatory relocations of people, a practice under fire as a means of establishing protected areas in India.

“Being able to move freely and safely from one habitat patch to another is vital if these creatures [are to] genetically expand their numbers”, says Chatchote Thitaram (Center of Excellence in Elephant Research and Education, Chiang Mai University, Thailand). “The corridors should also dramatically reduce elephant–human conflict.”

Certain trees keep cities cooler

Ilima Loomis

To help keep cities cool, plant trees that have dense foliage and exhibit higher rates of transpiration. That's the takeaway from a recent study by German researchers (Landscape Urban Plan 2015; doi:10.1016/j.landurbplan.2015.06.005).

It's long been known that trees play a key role in reducing heat in densely populated, mainly paved urban areas. But this new investigation helps explain how this heat reduction works, and what kinds of trees are best for keeping areas cool. The researchers showed that urban trees promote surface cooling by shading people and the ground and reducing the heat that one feels radiating off impervious surfaces. They also confirmed that transpiration is an important component of trees' cooling abilities, finding that trees with higher transpiration rates are better at lowering temperatures.

“When water evaporates, energy is released at the leaf cell and atmosphere interface”, says Sten Gillner, a forest scientist at the Institute of Forest Botany and Forest Zoology (Tharandt, Germany) and lead author on the paper. “In this exothermic [process], the energy is taken from the leaf and given to the water molecules, contributing to air cooling.”

Of the six species studied, hazels (Corylus colurna) and the small-leafed linden (Tilia cordata) offered the greatest cooling benefits, reducing surface temperatures by a median of 15°C and 13°C, respectively. In contrast, Dutch elms (Ulmus × hollandica) were the least cooling of the group, as they were associated with only a 6°C median reduction. The researchers emphasized that urban planners should select trees that are well-adapted to their particular area, avoiding species that lose foliage in drought, for example.

Roland Ennos, an environmental physicist at the University of Hull (Hull, UK), notes that this German study was one of the first to show that trees differ in their cooling benefits. Ennos believes this and similar work provides evidence to support tree-planting programs at the government level. “This is an example of the growing amount of useful research that actually goes out into the streets and measures what vegetation can do for us”, he says.

India introduces real-time pollutant monitoring

Dinesh C Sharma

To improve compliance with domestic laws regulating air and water pollution, India's Central Pollution Control Board (CPCB) has mandated that all major industrial units install automated systems for continuous real-time monitoring of their discharged wastes. Instead of sending inspectors to collect random samples at sites for later testing in laboratories – or depending on industry-supplied data – the CPCB has put the onus on companies to monitor effluents for parameters such as pH, total organic carbon, and total suspended solids, as well as for chemicals such as ammonia and nitrates. All information is then transmitted directly to state-level pollution control boards, with the costs of purchasing and maintaining the monitoring equipment borne by the companies themselves.

About 2800 industries in various sectors (textile, pharmaceuticals, leather, sugar, paper, etc) are covered under the new monitoring requirements, as are sewage treatment plants operated by local government agencies. “Nearly 50% of the [affected companies] have moved toward compliance”, Environment Minister Prakash Javadekar noted in a statement, adding that this shift represents a “big leap in the country's management of pollution”. However, several industries have sought an extension of the September 30th 2015 compliance deadline, and many smaller firms have requested exemption from real-time monitoring, citing the prohibitive costs of buying the necessary equipment.

“Pollution control boards set conditions for quality of waste discharge while giving ‘consent to operate’ to any industry. But due to a shortage of monitoring staff and reluctance of industries to operate the monitoring equipment at all times, the quality of discharge from industries does not, in many cases, conform to the stipulated conditions”, says Syamal Kumar Sarkar, Distinguished Fellow of The Energy and Resources Institute (New Delhi, India). Partially treated or untreated water finds its way into rivers like the Ganges and other water bodies.

Experts suggest that more thorough regulatory reforms are required. “The new system will not work unless we're able to make the regulatory system transparent, participatory, and accountable at every level. One way to do this would be to appoint empowered management committees, which should have access to all data and to which the pollution control boards are made accountable”, suggests Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People (New Delhi, India). Sarkar wants to see the capacity of the boards enhanced, to enable them to effectively monitor large volumes of pollution data and to initiate regulatory action based on that data.

Erosion may undermine reef resilience

Christie Wilcox

In anticipation of rising sea-surface temperatures and increasing ocean acidification, scientists are racing against the clock to understand how complex marine ecosystems will respond to climate change. Coral reefs are of particular concern; some studies have predicted widespread bleaching and death, while others have found coral species to be more resilient than anticipated. But new research suggests high hopes may be premature, given that reef erosion appears to be more strongly driven by changes in pH than is growth.

Previous studies examining climate-change effects on reefs largely focused on reef-building corals, though the net growth of reefs relies on the delicate interplay between corals, secondary marine calcifiers such as crustose coralline algae, and organisms such as bioeroding worms that bore into coral skeletons and tear down reef structures. In a yet-to-be peer-reviewed preprint posted in June (PeerJ PrePrints 2015; doi:10.7287/peerj.preprints.11 90v1), an international team of scientists describes the novel use of microcomputed tomography, or μCT, to simultaneously measure both secondary accretion (by organisms other than corals) and bioerosion along a natural environmental gradient in Kaneohe Bay, on the Hawaiian island of Oahu, which varied in depth, temperature, nutrients, and pH. Calcium carbonate blocks cut from dead Porites coral skeletons were placed along a 34-m transect and left undisturbed for a little over a year. The μCT scanning technology, used at the Cornell Imaging Multiscale CT facility, is functionally similar to the medical CAT scan used to investigate head injuries, and allowed the scientists to examine the experimental blocks inside and out, both before and after deployment, generating three-dimensional images of any changes that occurred in situ.

Figure 4.

An experimental block being secured at the reef site off Oahu.

The authors discovered that accretion and erosion respond differently to environmental variables including pH, with erosion much more strongly linked to acidity than previously documented. “Models predicting the impact of climate change on coral reefs often lump accretion and erosion processes together”, explains lead author Nyssa Silbiger (University of Hawaii, Manoa), “but the fact that we found different drivers means that we need to think more deeply about the predictive models we're using”.

Ultimately, the strong relationship between erosion and acidity spells trouble for coral reefs. “If erosion keeps increasing [with increased partial pressure of CO2], reefs will switch from net accretion to net erosion” no matter how resilient the corals are, warns Silbiger. Still, she's optimistic. “I think there's a lot more to learn before we can say that reefs are going to disappear.”

Warm, salty wetlands could be key to fighting chytrid

Patrick Monahan

Visitors to southeastern Australia's pristine wetlands don't often get to hear the distinctive call (http://bit.ly/1HLP1xE) of the endangered growling grass frog (Litoria raniformis) – but their growls might be heard near abandoned, water-filled quarries. New research reveals that such warm and saline ponds, although at first glance seemingly less than ideal, may serve as a refuge from the amphibian-killing fungus Batrachochytrium dendrobatidis, or chytrid (Ecol Lett 2015; doi:10.1111/ele.12463).

Study author Geoff Heard, a Research Fellow at the University of Melbourne (Parkville, Australia), and his colleagues suspected that the chytrid fungus – one of the main drivers of amphibian extinctions worldwide – might be behind recent L raniformis population losses. “Chytrid was something we knew was probably involved in the decline of this species but we didn't know much about it”, says Heard. After 11 years of monitoring and swabbing frogs to detect possible infections, the scientists discovered that chytrid prevalence was far lower in water bodies characterized by higher temperature and salinity – so-called “refugial” wetlands – and that frog populations in these habitats were three times more likely to survive each year as compared with populations elsewhere in the study area. “It solves the questions we had about why these frogs were doing so well in warm and salty quarries that, at face value, don't look particularly great.”

Figure 5.

Certain types of wetlands offer growling grass frogs refuge from B dendrobatidis.

To conserve endangered species, however, population dynamics at a larger scale must also be considered. Within networks of ponds, sites where populations are extirpated may later be recolonized by frogs from the surrounding area. Crucially, Heard and his co-authors also showed that when these larger pond networks included refugial habitats, growling grass frogs were more likely to persist.

Learning how environmental characteristics influence disease opens up new options for managing wetlands to aid amphibians. Activities like trimming the canopy over ponds, for example, could increase the amount of direct sunlight received, leading to elevated water temperatures that might help stave off chytrid. Heard continues, “The exciting thing for me is that we have straightforward and tangible capacities to manipulate temperature, in particular, to give endangered frogs a helping hand”.

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