Water management planning approach deals with deep uncertainties

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Issue 409, 26 March 2015

 Science for Environment Policy

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Water management planning approach deals with deep uncertainties
More adaptive approaches to planning could help policymakers deal with deep uncertainties about the future of our planet. Researchers have developed a method for adaptive planning which they suggest could protect against failure when future predictions turn out to be inaccurate. They illustrate their approach using the case of water management in the Rhine Delta region of the Netherlands.
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Rooftop gardens could grow three quarters of city’s vegetables
Rooftop gardens in cities could provide more than three quarters of the vegetables consumed in them, a case study from Bologna, Italy, suggests. If all suitable flat roof space was used for urban agriculture, rooftop gardens in the city could supply around 12 500 tons of vegetables a year whilst also providing a range of ecosystem services, the researchers say.
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Bee and wasp extinctions in UK driven by historical agricultural changes
Changes in agricultural policy and practice, such as increased intensification and fertiliser use, are responsible for many historical extinctions of pollinator populations in the UK, suggests new research. The study looked at bee and wasp extinction rates in relation to agricultural practices since the mid-19th century.
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Arctic ice melt affects seabird feeding behaviour
Virtually sea ice-free summers since 2005 have forced an important Arctic seabird species to change its foraging grounds and prey, new research shows. The body mass of the little auk — the most abundant seabird in the Atlantic Arctic — has shrunk by 4% in the past 20 years in one of its Russian breeding grounds, the study found. This change may be caused by its new foraging behaviour.
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Water management planning approach deals with deep uncertainties

More adaptive approaches to planning could help policymakers deal with deep uncertainties about the future of our planet. Researchers have developed a method for adaptive planning which they suggest could protect against failure when future predictions turn out to be inaccurate. They illustrate their approach using the case of water management in the Rhine Delta region of the Netherlands.

It is difficult to know or predict exactly what the world will be like in the future. Faced with uncertainty, policymakers often make plans based on the most accurate predictions available. However, if the future does not turn out as predicted, even the best plans for that future will fail. It might be better to incorporate flexibility into planning from the outset, to enable planners to deal with a range of futures.

In developing their method, the researchers began by describing two existing adaptive planning approaches. The first, the Adaptive Policymaking method, is a step-by-step process for developing a basic plan along with contingency plans that allow for adaptation as time goes on. The second method, Adaptation Pathways, involves creating a plan as a map of various actions that can be followed or introduced later depending on progress towards targets.

They integrated the two methods to create a new approach that they call ‘Dynamic Adaptive Policy Pathways’ for planning in situations of deep uncertainty. They illustrated how this approach could be used by developing a long-term water management plan for the Rhine Delta region which faces an uncertain future due to climate change.

The first step in their process is to describe the current situation in the region, including constraints and uncertainties, as well as a definition of a successful outcome. For example, in the Rhine Delta region, they defined success as there being enough freshwater and no flooding for the next 100 years. Under the Water Framework Directive1, success would also depend on there being no negative impacts on nature.

Step two is a problem analysis. In the case of the Rhine Delta, they focused on coastal flooding, which causes saltwater intrusion and, during dry periods, a lack of water for purposes including irrigation. Due to uncertainties in climate predictions, it is not clear how serious these problems will become in the future and when this may occur. The researchers therefore considered future scenarios covering a range of different climate and population growth scenarios for the Netherlands.

In further steps, the researchers suggested ten potential actions and assessed their effectiveness. They gave the actions ‘sell-by dates’, which indicate when changes might be needed if targets are not met. For instance, they suggested using existing infrastructure to allow water levels to increase by 10 cm in the Rhine Delta. This is a low-cost option for dealing with flooding, but has a short sell-by date of 2050–2060. Meanwhile, increasing cultivation of salt- and drought-tolerant crops is costly, but has a sell-by date past 2100. In a fifth step, the researchers plotted the most logical pathways through these actions — each pathway is a series of different actions that should lead to success of the plan overall.

The next three steps involve selecting the preferred pathways, determining ‘signposts’ and ‘triggers’ that indicate that a sell-by date will be reached. The pathways specify a plan for initial actions, along with options to cover a range of future scenarios. Theoretically, the plan would be implemented along with a monitoring programme, which in the Rhine Delta case would monitor sea-level rise and changes in regional water demands.

According to the researchers, although their approach is complex, it encourages planners to consider adaptation over time at the outset. The plan they developed has been used as inspiration for Adaptive Delta Management in the Netherlands, which is the cornerstone of the climate adaptation strategy in the Dutch Delta Programme.

1. http://ec.europa.eu/environment/water/water-framework/index_en.html

Source: Haasnoot, M., Kwakkel, J. H., Walker, W. E. et al. (2013). Dynamic adaptive policy pathways: A method for crafting robust decisions for a deeply uncertain world. Global Environmental Change 23(2): 485–498. DOI:10.1016/j.gloenvcha.2012.12.006.

Contact: [email protected]

Read more about: Sustainable development and policy assessment, Water


 

Rooftop gardens could grow three quarters of city’s vegetables

Rooftop gardens in cities could provide more than three quarters of the vegetables consumed in them, a case study from Bologna, Italy, suggests. If all suitable flat roof space was used for urban agriculture, rooftop gardens in the city could supply around 12 500 tons of vegetables a year whilst also providing a range of ecosystem services, the researchers say.

Any unused roof space in a city represents an opportunity to add to that city’s green infrastructure. Urban green spaces and infrastructure, which include rooftop gardens, offer benefits for both wildlife and people. Not only can they produce food for city-dwellers, they can increase urban biodiversity and link together to form green networks, acting as corridors for wildlife. They can also reduce a city’s ecological footprint by filtering polluted air, absorbing noise and CO2 emissions, and controlling temperature by shading.

In 2010, Bologna became the first Italian city to test rooftop vegetable gardens on public buildings, as part of a project led by the local authority, university and a non-profit organisation. Researchers followed the trial over three years between 2012 and 2014.

During this time, rooftop gardeners grew lettuce, black cabbage, chicory, tomato, aubergine, chili pepper, melon and watermelon, either in plastic pipes, recycled pallets filled with compost or on polystyrene panels floating in tanks, also made from recycled pallets.

On average, the recycled pallet system with compost produced the most vegetables for the amount of space used, a third more than the floating system and more than twice that of the pipe system. However, the amount of each type of vegetable produced by each system in each season varied considerably and the pipe system made use of hanging space when surface area was limited.

From the results of the trials, the researchers were able to design an optimal growing system for a 216 m2 rooftop garden, which combined elements of each system in order to maximise productivity throughout the year. This included slightly more floating structures than pallets, as well as pipe systems along the railings. The researchers estimate that this hypothetical garden could produce more than three tonnes of vegetables per year.

Next, the researchers estimated the potential productivity of a network of vegetable gardens occupying all suitable flat roof space across the city. They used digital maps and computer-aided design (CAD) software to identify all the unused flat spaces on Bologna’s roofs and terraces.

Their calculations suggest that, if all available space (about 0.82 km2) was utilised, rooftop gardens in Bologna could produce around 12,500 tonnes of vegetables. This means that, based on actual consumption data for the city, rooftop gardens could meet 77% of residents’ needs for vegetables.

If all the spaces identified in the study were turned into gardens, they could capture an estimated 624 tons of CO2 each year. The study’s authors also mapped the connections between spaces that were within 500 m of each other showing that rooftop gardens could create a network with a total length of 94 km of green corridors for wildlife, including pollinating insects. The 500 m distance was considered appropriate by the researchers because most common bee pollinators have a flight foraging distance of 750–1500 m.

Source: Orsini, F., Gasperi, D., Marchetti, L., et al. (2014). Exploring the production capacity of rooftop gardens (RTGs) in urban agriculture: the potential impact on food and nutrition security, biodiversity and other ecosystem services in the city of Bologna. Food Security 6(6): 781-792. DOI: 10.1007/s12571-014-0389-6.

Contact: [email protected]

Read more about: Agriculture; Green infrastructure; Urban environment


 

Bee and wasp extinctions in UK driven by historical agricultural changes

Changes in agricultural policy and practice, such as increased intensification and fertiliser use, are responsible for many historical extinctions of pollinator populations in the UK, suggests new research. The study looked at bee and wasp extinction rates in relation to agricultural practices since the mid-19th century.

The pollination services provided by insects, such as bees and flower-visiting wasps, are fundamental to maintaining both biodiversity and agricultural productivity. However, despite their importance, human activities are causing the number and diversity of these species to decline.

Many studies have focused on understanding how habitat destruction, loss of the flowers these species rely on for survival and increased use of pesticides have contributed to the decline in these species. However, much of this research has been relatively limited in terms of the time periods and geographical ranges considered.

In this research, almost 500 000 records of sightings held by the Bees, Wasps and Ants Recording Society (BWARS) were used to assess the extinction of bee and flower-visiting wasp species throughout Britain from the mid-19th century to the modern day. The researchers examined the rate of extinctions and how it varied over time, looking for patterns to help explain changes.

Species were considered as extinct in the UK if there had been no record of them for 20 or more years. Many of the species examined still exist in continental Europe; as such, these are species which have only become locally extinct in Britain.

A total of 23 species were identified as extinct. The years that these species were last observed ranged from as long ago as 1853, to as recently as 1990. The rate of extinctions varied over time, with four periods of extinction rate change identified. These were from 1874 to 1928, 1928 to 1958, 1958 to 1986 and 1986 onwards.

The researchers linked these periods of increased extinction to phases of large-scale changes in agricultural policy and practice. The 1874 period of species loss, when 0.96 species were lost per decade (compared with 0.21 before that) coincided with changes in fertiliser use. These reduced the need for ‘fallow’ years to maintain soil quality, when the wild plants some species relied on would normally flourish.

A major period of species loss — 3.46 species per decade — occurred from around 1928 to 1958, following changes to agricultural policy and practice after the First World War. During this period, agriculture was intensified due to food security concerns, which continued through to the Second World War and beyond.

Between 1958 and 1986, the extinction rate slowed to around 0.98 species per decade. This is not easily explained, the study’s authors say, since agriculture became even more intensive during this period. However, it may be that the species most sensitive to change had already being lost, while less sensitive species survived.

The final period, from 1986 to 1994, saw an extinction rate of 5.48 species per decade. The authors note the high uncertainty associated with this particular figure and acknowledge that this result may appear to contradict recent reports of reduced species loss. They suggest this high rate may be due to four extinctions between 1988 and 1990 which skew the data and exaggerate the estimate. Between 1971 and 1994 there were otherwise no extinctions.

Overall, the study shows that, while the drivers behind the extinctions are complex, they are strongly linked with changes in agricultural policy and practice.

Source: Ollerton, J., Erenler, H., Edwards, M., Crockett, R. (2014) Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes. Science 346(6215): 1360–1362. DOI:10.1126/science.1257259.

Contact: [email protected]uk

Read more about: Agriculture, Biodiversity


 

Arctic ice melt affects seabird feeding behaviour

Virtually sea ice-free summers since 2005 have forced an important Arctic seabird species to change its foraging grounds and prey, new research shows. The body mass of the little auk — the most abundant seabird in the Atlantic Arctic — has shrunk by 4% in the past 20 years in one of its Russian breeding grounds, the study found. This change may be caused by its new foraging behaviour.

Understanding the impacts of changes in the cryosphere — the Earth’s frozen regions — on Arctic biodiversity has been identified as a major scientific challenge by organisations including the Arctic Council. Like polar bears, little auks (Alle alle) are an important Arctic ‘sentinel species’, this study explains. This means that any changes to this species, such as behavioural or population change, may send advance warning signals to the wider world that the birds’ environment is changing.

Globally, there are around 40 million little auks and they play an important role in marine ecosystems, preying on zooplankton. They breed on islands around the Arctic and migrate south in winter to the North Sea.

The researchers studied the species in their most northerly habitat, the remote Franz-Josef Land islands of Russia, during the summer of 2013. They measured the bodies of 108 individuals and assessed foraging behaviour by placing movement monitors on 15 individuals as well as by watching birds’ diving behaviour. In addition, 20 adult birds were captured to identify which prey species they had caught and were carrying back in special pouches for their chicks back on land.

The results indicate that the average body mass of the population has shrunk by 4% since 1992, when a similar study was conducted at the same location. In addition, their prey had changed since another earlier study from 1991–1993, also at the same site. In the current study, nearly all prey (97.5%) were copepod species of plankton. In the 1991–1993 study, the auks also ate copepods, but 13% of their diet was a small crustacean called Apherusa glacialis.

Foraging behaviour also differed to the behaviour of little auk populations observed by scientists in other locations. Birds in this study spent much less time flying per foraging trip, because they fed extremely close to their nesting colonies, unlike populations in Greenland and Svalbard (Norway) which feed offshore.

The researchers attribute these results to changes in sea ice cover in recent years. Little auks normally feed on prey species that are found in cold water around the edge of sea ice. However, satellite images show that the region has been almost ice-free in August every year since 2003–2004, because sea ice is melting earlier each year. Previously, between 1979 and 2003, images show that sea ice covered 55–70% of the area every year in August.

Fortunately, the little auk is an adaptable species and has been able to find new, closer foraging grounds in meltwater around a local glacier. This has allowed the birds to maintain chick growth rate, but has led to the decline in adult body mass. The study notes that the glacier has shrunk by 9% since 1994, however, so this feeding option is only available for as long as the glacier survives.

The study’s authors conclude that species’ adaptable behaviour needs to be considered in computer models that predict the future distributions of species under climate change.

Source: Grémillet, D., Fort, J., Amélineau, F. et al. (2015). Arctic warming: nonlinear impacts of sea-ice and glacier melt on seabird foraging. Global Change Biology. DOI:10.1111/gcb.1281.

Contact: [email protected]

Read more about: Biodiversity, Marine ecosystems


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