Anthropocentric N2O Perturbations

Recent studies have shown that human nitrogen additions to terrestrial eco-systems increase the terrestrial carbon dioxide uptake from the atmosphere. A new study published online this week in Nature Geoscience reports now that the climatic benefits from carbon sequestration are largely offset by increased nitrous oxide emissions, a further side-effect of human nitrogen additions to terrestrial ecosystems.

Human activities have more than doubled nitrogen inputs to the terrestrial biosphere since the 1860s. The two main causes for this are increased atmos-pheric nitrogen deposition from, for instance, fossil fuel burning, and the ap-plication of fertilizers in agriculture. Nitrogen is an essential nutrient for plant and microbial growth, and one of the key limiting nutrients in many natural ecosystems.

The anthropogenic perturbations of the nitrogen cycle are known to affect the terrestrial sources and sinks of greenhouse gases such as carbon dioxide (CO2) and nitrous oxide (N2O). These changes are potentially very im-portant as they may significantly affect the climate system, but their magni-tude is still unknown.

“When added to nitrogen-limited ecosystems, it [nitrogen] can stimulate plant growth and/or suppress soil respiration, thereby leading to increased ecosys-tem carbon storage” explains Sönke Zaehle. However, there are also potentially negative consequences for adding nitrogen to ecosystems, as increasing nitrogen availability may enhance nitrogen losses from ecosystems, and eventually even have damaging effects on plant health. Particularly relevant for climate are elevated emissions of nitrous oxide, a long-lived greenhouse gas that is emitted from fertilised fields, as well as nitrogen-rich forest and grassland ecosystems.

Drawing on reconstructions of past and present anthropogenic nitrogen deposition and fertiliser applica-tions, Sönke Zaehle and colleagues used a global computer model of the coupled terrestrial carbon and nitrogen cycles to better understand the consequences of this anthropogenic nitrogen perturbation for the climate system. Their results confirm that the anthropogenic nitrogen perturbation has profoundly affected terrestrial carbon dioxide and nitrous oxide fluxes. Human nitrogen additions are the principle cause for the increase in terrestrial nitrous oxide emission since 1960, and contribute to about one fifth of the current global net carbon uptake (1996-2005).

Sönke Zaehle and colleagues then determined the effect of anthropogenic nitrogen on the atmospheric concentrations of the greenhouse gases CO2 and N2O, and assessed the resulting consequences for pre-sent-day climate. The key finding is that the climatic effects of the anthropogenic nitrogen perturbation from both gases are very substantial but of opposite signs. The cooling effect due to enhanced carbon uptake of the terrestrial biosphere is more than compensated for by the warming effects from enhanced terrestrial N2O emissions.

Contacts and sources: 

Max Planck Institute for Biogeochemistry

70% Of 8-Month-Olds Consume Too Much Salt

Seventy per cent of eight-month-old babies have a salt (sodium chloride) intake higher than the recommended UK maximum level, due to being fed salty and processed foods like yeast extract, gravy, baked beans and tinned spaghetti.

Many are also given cows' milk, which has higher levels of salt than breast or formula milk, as their main drink despite recommendations that it should not be used in this way until babies are at least one year old. High levels of salt can damage developing kidneys, give children a taste for salty foods and establish poor eating practices that continue into adulthood and can result in health problems later in life.

These are the latest findings from researchers at the University of Bristol based on almost 1,200 participants in the Children of the 90s study and just published online by the European Journal of Clinical Nutrition.

The researchers found that the majority of infants were first introduced to solids around 3-4 months, with the mean salt intake for the highest group at 8 months more than double the maximum recommendation for that age group (400mg sodium per day up to 12 months). Infants in this top group often consumed cows' milk as a main drink, which has a higher sodium content at 55mg per 100g than breast (15mg per 100g) or formula (15-30mg per 100ml) milk. They also ate three times the amount of bread compared to the lowest group, and were given salty flavourings such as yeast extract and gravy.

In the UK, the majority of salt consumed by individuals is added to food during manufacturing, with a relatively small proportion added during cooking or at the table and current intakes in both children and adults are far higher than NICE (National Institute for Health and Clinical Excellence) guidelines.

Speaking about the findings, Dr Pauline Emmett and Vicky Cribb, the nutritionists who conducted the research, said:

'These findings show that salt intakes need to be substantially reduced in children of this age group. Infants need foods specifically prepared for them without added salt, so it is important to adapt the family diet.

'This research suggests that clear advice is needed for parents about what foods are suitable for infants. This should be given to all parents and carers and should include the important advice not to use cows' milk as a main drink before 12 months of age.'

They added that:

'Given that three-quarters of salt in the diet comes from processed adult foods, successful salt-reduction strategies can only be achieved with the co-operation of the food industry. Manufacturers have a responsibility to reduce the salt content of food products. This process has already started in UK but much more needs to be done. If this study were repeated today it is likely that there would be some improvement but not enough to safeguard the health of all babies. '

The researchers studied three-day dietary records (completed by the mothers) of 1,178 8-month-old infants born in 1991/92 and involved in the Children of the 90s study at the University of Bristol. Infants were categorised into four groups of increasing salt intake.

Contacts and sources:
Dara O'Hare
University of Bristol

Cranky, Grumpy, Fearful Or Moody: Tailored Parenting Style For Particular Personality Halves Depression In Kids

When it comes to rearing children, just about any parent will say that what works with one kid might not work with another. Parents use all sorts of strategies to keep kids from being cranky, grumpy, fearful or moody, while encouraging them to be independent, creative and well-adjusted.

Starry Night by Vincent Van Gogh

Image: Wikipedia

But which parenting styles work best with which kids? A study by University of Washington psychologists provides advice about tailoring parenting to children's personalities.

At the end of the three-year study, the psychologists found that the right match between parenting styles and the child's personality led to half as many depression and anxiety symptoms in school-aged children. But mismatches led to twice as many depression and anxiety symptoms during the same three years.

The study was published online Aug. 1 in the Journal of Abnormal Child Psychology.

"This study moves away from the one-size-fits-all approach to parenting, and gives specific advice to parents on how to mitigate their child's anxiety and depression," said Cara Kiff, lead author and psychology resident at the UW School of Medicine. "We're considering characteristics that make children vulnerable to anxiety and depression, and factoring in how that shapes how kids react to different parenting approaches."

"We hear a lot about over-involved parents, like 'tiger moms' and 'helicopter parents,'" said co-author Liliana Lengua, a UW psychology professor. "It is parents' instinct to help and support their children in some way, but it's not always clear how to intervene in the best way. This research shows that parenting is a balance between stepping in and stepping out with guidance, support and structure based on cues from kids."

Kiff, Lengua and Nicole Bush, a co-author and postdoctoral fellow at University of California, San Francisco's Center for Health and Community, studied interactions between 214 children and their mothers during interviews at home. An almost even mix of boys and girls participated in the study and were, on average, 9 years old when the study began.

The children and their mothers met with the researchers once a year. The researchers observed as the pairs discussed neutral topics, such as a recap of the day's events, and common problems, like conflicts over homework and chores. During the conversations, the researchers noted parenting styles, including warmth and hostility, and how much mothers allowed their child to guide the conversations – an autonomy-granting parenting style.

The researchers also measured the children's anxiety and depression symptoms and evaluated their personality characteristics. They paid particular attention to effortful control, the kids' abilities to regulate their own emotions and actions, which is associated with lower levels of depression and anxiety.

At the end of the three-year study, the researchers found that

• Children with greater effortful control had fewer symptoms of anxiety and depression compared with other kids in the study, and those symptoms usually remained low regardless of parenting style.
• When children were higher in effortful control but their parents used higher levels of guidance or provided little autonomy, those children showed higher levels of depression and anxiety.
• Children with low effortful control had less anxiety when mothers provided more structuring and less autonomy.
• Children low in effortful control doubled their anxiety symptoms if they had mothers who provided little control.

Lengua, who is also the director of the UW Center for Child and Family Well-Being, said the study shows how parents can use their child's personality and temperament to decide how much and what type of help to give. For some kids, particularly those who have trouble regulating their emotions, more help is good. But for kids who have pretty good self-control, too much parental control can lead to more anxiety and depression.

The results were somewhat surprising, Lengua said, because parents of children at this age are typically told to give their kids more autonomy as they learn to navigate social situations and make decisions about schedules and homework. This can butt against parents' intuition to assist kids through trickier situations.

"Parents should be there to help – but not take over – in difficult situations and help their children learn to navigate challenges on their own," Lengua said.

The National Institute of Mental Health funded the study.

Contacts and sources:

Molly McElroy
University of Washington