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A continuous data set of Greenland Ice Sheet altimeter height from European Remote Sensing satellites (ERS-1 and ERS-2), 1992 to 2003, has been analyzed. An increase of 6.4 +/- 0.2 centimeters per year (cm/year) is found in the vast interior areas above 1500 meters, in contrast to previous reports of high-elevation balance. Below 1500 meters, the elevation-change rate is -2.0 +/- 0.9 cm/year, in qualitative agreement with reported thinning in the ice-sheet margins. Averaged over the study area, the increase is 5.4 +/- 0.2 cm/year, or approximately 60 cm over 11 years, or approximately 54 cm when corrected for isostatic uplift. Winter elevation changes are shown to be linked to the North Atlantic Oscillation.

The genome of the invertebrate chordate Ciona intestinalis was found to be a stable mosaic of methylated and nonmethylated domains. Multiple copies of an apparently active long terminal repeat retrotransposon and a long interspersed element are nonmethylated and a large fraction of abundant short interspersed elements are also methylation free. Genes, by contrast, are predominantly methylated. These data are incompatible with the genome defense model, which proposes that DNA methylation in animals is primarily targeted to endogenous transposable elements. Cytosine methylation in this urochordate may be preferentially directed to genes.

The self-splicing bl1 intron lariat from mitochondria of Saccharomyces cerevisiae catalyzed the insertion of nucleotidyl monomers derived from the 3' end of a donor RNA into an acceptor RNA in a 3' to 5' direction in vitro. In this catalyzed reaction, the site specificity provided by intermolecular base pair interactions, the formation of chimeric intermediates, the polarity of the nucleotidyl insertion, and its reversibility all resemble such properties in previously proposed models of RNA editing in kinetoplastid mitochondria. These results suggest that RNA editing occurs by way of a concerted, two-step transesterification mechanism and that RNA splicing and RNA editing might be prebiotically related mechanisms; possibly, both evolved from a primordial demand for self-replication.

Targeted decommissioning of deteriorated and obsolete infrastructure can provide opportunities for restoring degraded ecosystems.

In their Perspective (“Restoration of ecosystem services for environmental markets,” 31 July, p. [575][1]), M. A. Palmer and S. Filoso call for direct measurement of ecosystem processes and third-party verification. This step is a critical one for the burgeoning compensatory mitigation industry to preserve, or recover, its credibility. However, Palmer and Filoso did not mention those who actually control ecosystem markets and did not consider how more rigorous restoration quality checks could provide an economic incentive to reduce ecosystem impacts in the first place. Ecosystem service markets are odd in that they are created and controlled by regulation. For aquatic ecosystems, for example, the Clean Water Act (CWA) and the first President Bush's administration created a cap-and-trade program for wetlands and later for streams. This produced a demand for restored ecosystems through fiat, not through an inherent consumer need for ecosystem service commodities. The U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (USACE) determine the presence of wetlands and streams on the landscape, their condition, and any requirements for compensation when these ecosystems are affected by development. Thus, by regulating the presence of existing wetlands and streams that might be affected, these two federal agencies are responsible for creating demand for these ecosystem services. In turn, these two agencies bear responsibility for the presence of the supply of restored ecosystem services through approval and certification of specific restoration projects. If the quality and integrity of restoration are lacking in existing aquatic ecosystem service markets, the blame rests largely on the shoulders of EPA and USACE, and these are the agencies through which aquatic ecosystem restoration policy changes must occur. We agree with Palmer and Filoso that more stringent criteria must be established for restoration as part of ecosystem markets, and we suggest that EPA and USACE quickly institute more stringent standards. But we also emphasize the economic and ecological implications of such changes. Making the success criteria of restoration more rigorous will undoubtedly increase the cost of restoration: Project engineering will initially prove more difficult and therefore more costly; financial risks will increase with greater uncertainty, causing investors to increase required rates of return; and verification of project success, whether direct or through third parties, will represent an additional expense. The net result is an increase in mitigation costs, which will need to be recouped by charging more for mitigation credits. This will, in turn, drive up the costs of affecting aquatic ecosystems, serving as a deterrent to damaging them. That is, increased restoration quality requirements could reduce the demand for compensatory mitigation by providing incentives for avoidance. This is likely the most substantial benefit of more expensive restoration. [1]: /lookup/doi/10.1126/science.1172976