New portrait of Earth shows land cover as never before

A new global portrait taken from space details Earth’s land cover with a resolution never before obtained. ESA, in partnership with the UN Food and Agriculture Organisation, presented the preliminary version of the map to scientists last week at the 2nd GlobCover User Consultation workshop held in Rome, Italy.

Earth’s land cover has been charted from space before, but this map, which will be made available to the public upon its completion in July, has a resolution 10 times sharper than any of its predecessors.

Scientists, who will use the data to plot worldwide land-cover trends, study natural and managed ecosystems and to model climate change extent and impacts, are hailing the product – generated under the ESA-initiated GlobCover project – as 'a milestone.'

"The GlobCover system is a great step forward in our capacities to automatically produce new global land cover products with a finer resolution and a more detailed thematic content than ever achieved in the past," Frédéric Achard of the European Commission's Joint Research Centre (JRC) said.

"This GlobCover product is much more than a map. It is an operational scientific and technical demonstration of the first automated land cover mapping on a global scale and may provide the detailed description of the land surface states needed for regional climate modelling," said Prof. Pierre Defourny, from the Université catholique de Louvain, who designed the land classification process.

"Land cover data is an essential requirement of the sustainable management of natural resources, environmental protection, food security, climate change and humanitarian programmes," John Latham of the Food and Agriculture Organisation (FAO) said.

"The GlobCover product will be the first freely available product at 300m resolution and is therefore a milestone product which will be fundamental to a broad level stakeholder community."

Jaap van Woerden from the United Nations Environment Programme (UNEP) said: "This map can greatly support the work of UNEP and partners in addressing environmental priority issues such as climate change and ecosystem management."

Prof. Christiane Schmullius from the University of Jena in Germany said the new GlobCover product “revolutionises global land cover mapping."

The map is based on 20 Terabytes of imagery – equivalent to the content of 20 million books – acquired from May 2005 to April 2006 by Envisat’s Medium Resolution Imaging Spectrometer (MERIS) instrument.

All images then undergo a standardised processing technique developed and operated by Medias-France/Postel, together with Brockmann Consult, the Université catholique de Louvain and partners.

There are 22 different land cover types shown in the map, including croplands, wetlands, forests, artificial surfaces, water bodies and permanent snow and ice. For maximum user benefit, the map’s thematic legend is compatible with the UN Land Cover Classification System (LCCS).

GlobCover, launched in 2005, is part of ESA’s Earth Observation Data User Element (DUE). An international network of partners is working with ESA on the project, including the UN Environment Programme (UNEP), FAO, the European Commission's Joint Research Centre (JRC), the European Environmental Agency (EEA), the International Geosphere-Biosphere Programme (IGBP) and the Global Observations of Forest Cover and Global Observations of Land Dynamics (GOFC-GOLD) Implementation Team Project Office.

Gene’s ‘selective signature’ aids detection of natural selection in microbial evolution

Scientists at MIT have come up with a mathematical approach for analyzing a protein simultaneously in a set of ecologically distinct species to identify occurrences of natural selection in an organism’s evolution.

The new method determines the “selective signature” of a gene, that is, the pattern of fast or slow evolution of that gene across a group of species, and uses that signature to infer gene function or to map changes to ecological shifts.

By reversing the usual order of inquiry—studying an organism, then trying to identify which genes are involved in a particular function—the scientists hope to hasten the understanding of microbial evolution by taking advantage of the nearly 2,500 microbes already sequenced.

“By comparing across species, we looked for changes in genes that reflect natural selection and then asked, ‘How does this gene relate to the ecology of the species it occurs in?’” said Eric Alm, the Doherty Assistant Professor of Ocean Utilization in the Department of Civil and Environmental Engineering. “The selective signature method also allows us to focus on a single species and better understand the selective pressures on it.”

“Our hope is that other researchers will take this tool and apply it to sets of related species with fully sequenced genomes to understand the genetic basis of that ecological divergence,” said graduate student B. Jesse Shapiro, who co-authored with Alm a paper published in the February issue of PLoS Genetics.

Their work also suggests that evolution occurs on functional modules—genes that may not sit together on the genome, but that encode proteins that perform similar functions.

“When we see similar results across all the genes in a pathway, it suggests the genomic landscape may be organized into functional modules even at the level of natural selection,” said Alm. “If that’s true, it may be easier than expected to understand the complex evolutionary pressures on a cell.”

“In a single species, a whole set of genes in the same module tend to change together,” said Shapiro. “Identifying these changes brings us a step closer to understanding the ecological basis of selection in a species and how changes at the genetic level affect the organisms interactions with its environment.”

For example, in Idiomarina loihiensis, a marine bacterium that has adapted to life near sulfurous hydrothermal vents in the ocean floor, the genes involved in metabolizing sugar and the amino acid phenylalanine underwent significant changes (over hundreds of millions of years) that may help the bacterium obtain carbon from amino acids rather than from sugars, a necessity for life in that ecological niche. In one of I. loihiensis’ sister species, Colwellia psychrerythraea, some of those same genes have been lost altogether, an indication that sugar metabolism is no longer important for Colwellia.

Shapiro and Alm focused on 744 protein families among 30 species of gamma-proteobacteria that shared a common ancestor roughly 1 to 2 billion years ago. These bacteria include the laboratory model organism E. coli, as well as intracellular parasites of aphids, pathogens like the bacteria that cause cholera, and soil and plant bacteria. They mapped the evolutionary distance of each species from the ancestor and incorporated information about the gene family (for instance, important proteins evolve more slowly than less vital ones) and the normal rate of evolution in a particular species’ genome in order to determine a gene’s selective signature.

“These are experiments we could never perform in a lab,” said Alm. “But Mother Nature has put genes into an environment and run an evolutionary experiment over billions of years. What we’re doing is mining that data to see if genes that perform a similar function, say motility, evolve at the same rate in different species. To the extent that they differ, it helps us to understand how change in core genes drives functional divergence between species across the tree of life.”

This work is part of the Virtual Institute for Microbial Stress and Survival. The research was also supported by additional grants from the U.S. Department of Energy Genomics: GTL Program, the National Institutes of Health, and a scholarship from the Natural Sciences and Engineering Research Council of Canada.

NIST finds 'metafilms' can shrink radio, radar devices

Recent research at the National Institute of Standards and Technology (NIST) has demonstrated that thin films made of “metamaterials”—manmade composites engineered to offer strange combinations of electromagnetic properties—can reduce the size of resonating circuits that generate microwaves. The work is a step forward in the worldwide quest to further shrink electronic devices such as cell phones, radios, and radar equipment.

Metamaterials may be best known as a possible means of “cloaking” to produce an illusion of invisibility, somewhat like the low-reflectivity coatings that help stealth fighter jets evade radar. As described in a new paper,* NIST researchers and collaborators performed calculations and simulations of two-dimensional surface versions, dubbed “metafilms,” composed of metallic patches or dielectric pucks. Vibrating particles in these metafilms cause incoming electromagnetic energy to behave in unique ways.

The researcher team deduced the effects of placing a metafilm across the inside center of a common type of resonator, a cavity in which microwaves continuously ricochet back and forth. Resonant cavities are used to tune microwave systems to radiate or detect specific frequencies. To resonate, the cavity’s main dimension must be at least half the wavelength of the desired frequency, so for a mobile phone operating at a frequency of 1 gigahertz, the resonator would be about 15 centimeters long. Other research groups have shown that filling part of the cavity with bulk metamaterials allows resonators to be shrunk beyond the usual size limit. The NIST team showed the same effect can be achieved with a single metafilm, which consumes less space, thus allowing for the possibility of smaller resonators, as well as less energy loss. More sophisticated metafilm designs would enhance the effect further so that, in principle, resonators could be made as small as desired, according to the paper.

The metafilm creates an illusion that the resonator is longer than its small physical size by shifting the phase of the electromagnetic energy as it passes through the metafilm, lead author Chris Holloway explains, as if space were expanded in the middle of the cavity. This occurs because the metafilm’s scattering structures, like atoms or molecules in conventional dielectric or magnetic materials, trap electric and magnetic energy locally. The microwaves respond to this uneven energy landscape by adjusting their phases to achieve stable resonance conditions inside the cavity.

On the downside, the researchers also found that, due to losses in the metafilm, smaller resonators have a lower quality factor, or ability to store energy. Accordingly, trade-offs need to be made in device design with respect to operating frequency, resonator size and quality factor, according to the paper. The authors include two from the University of Pennsylvania and a guest researcher from the University of Colorado.