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Posts Tagged ‘land-use change’

Forests Can No Longer Be Considered Wilderness: Study

Posted by feww on March 21, 2015

Deforestation: 70 percent of remaining forests less than 800m deep

Seventy percent of forests left on the planet are within 800 meters (0.5 mile) of a forest edge due to land use changes, especially encroaching urban, suburban developments and agriculture, which are causing global declines in biodiversity, according to a new study lead by North Carolina University.

The researchers discovered that very few forest lands are unaffected by some kind of human development.

“The loss of area, increase in isolation, and greater exposure to human land uses along fragment edges initiate long-term changes to the structure and function of the remaining fragments.”

They also conducted major experiments across five continents examining the effects of habitat fragmentation. They found that fragmented habitats reduce the diversity of plants and animals by up to 75 percent, with the smallest, most isolated patches causing the most impact.

“The initial negative effects were unsurprising,” said the corresponding author of the paper, a professor at NC State University. “But I was blown away by the fact that these negative effects became even more negative with time. Some results showed a 50 percent or higher decline in plant and animals species over an average of just 20 years, for example. And the trajectory is still spiraling downward.”

“Data from 76 different studies across the five longest-running experiments were drawn from published and unpublished sources (table S1). We synthesized results according to three fragmentation treatments: reduced fragment area [the focus of Biological Dynamics of Forest Fragments Project (BDFFP), Wog Wog, and Kansas; see Fig. 2 for identifiers of experiments], increased fragment isolation [Savannah River Site (SRS) and Moss], and increased proportion of edge (all experiments). Fragmented treatments were compared directly to non- or less-fragmented habitats that were either larger or connected via structural corridors (table S1).”

“The results were astounding,” said the author. “Nearly 20 percent of the world’s remaining forest is the distance of a football field—or about 100 meters—away from a forest edge. Seventy percent of forest lands are within a half-mile of a forest edge. That means almost no forest can really be considered wilderness.”

Research Article: Habitat fragmentation and its lasting impact on Earth’s ecosystems
Supplementary material for this article is available at

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GHG Concentrations Climbed to New Highs in 2012: WMO

Posted by feww on November 6, 2013

Atmospheric greenhouse gases reached new record levels

Atmospheric concentrations of major greenhouse gases responsible for climate change climbed to new records in 2012, according to WMO Greenhouse Gas Bulletin (No. 9: November 2013) released by the World Meteorological Organisation (WMO).

Levels of CO2, the primary greenhouse gas produced by human activities, grew by 2.2 ppm, higher the average of 2.02 ppm over the past decade. At 393.1 parts per million (ppm), the 2012 CO2 concentrations were 41 percent above the pre-industrial level.

The latest analysis of observations from the WMO Global Atmosphere Watch (GAW) Programme shows that the globally averaged mole fractions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) reached new highs in 2012, with CO2 at 393.1±0.1 ppm, CH4 at 1819±1 ppb and N2O at 325.1±0.1 ppb. These values constitute, respectively, 141%, 260% and 120% of pre-industrial (before 1750) levels. The atmospheric increase of CO2 from 2011 to 2012 is higher than the average growth rate over the past 10 years. For N2O the increase from 2011 to 2012 is smaller than the one observed from 2010 to 2011 but larger than the average growth rate over the past 10 years. Atmospheric CH4 continued to increase at a rate similar to the one observed over the past 4 years. The National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index shows that from 1990 to 2012 radiative forcing by long-lived greenhouse gases increased by 32%, with CO2 accounting for about 80% of this increase.

This ninth WMO/GAW Annual GHG Bulletin reports atmospheric abundances and rates of change of the most
important long-lived greenhouse gases (LLGHGs) – carbon dioxide, methane, nitrous oxide – and provides a summary of the contributions of the other gases. These three together with CFC-12 and CFC-11 account for approximately 96% of radiative forcing due to LLGHGs.

The NOAA Annual Greenhouse Gas Index (AGGI) in 2012 was 1.32, representing a 32% increase in total radiative forcing (relative to 1750) by all LLGHGs since 1990 and a 1.2% increase from 2011 to 2012 (Figure 1). The total radiative forcing by all LLGHGs in 2012 corresponds to a CO2-equivalent mole fraction of 475.6 ppm (

 Carbon dioxide (CO2) is the single most important anthropogenic GHG in the atmosphere

Carbon dioxide is the single most important anthropogenic greenhouse gas in the atmosphere, contributing ~64%  to radiative forcing by LLGHGs. It is responsible for ~84% of the increase in radiative forcing over the past decade and ~82% over the past five years. The pre-industrial level of ~278 ppm represented a balance of fluxes between the atmosphere, the oceans and the biosphere. Atmospheric CO2 reached 141% of the pre-industrial level in 2012, primarily because of emissions from combustion of fossil fuels (fossil fuel CO2 emissions 9.5±0.5 PgC in 2011, according to, deforestation and other land-use change (0.9±0.5 PgC in 2011). The average increase in atmospheric CO2 from pre-industrial time corresponds to ~55% of the CO2 emitted by fossil fuel combustion with the remaining ~45% removed by the oceans and the terrestrial biosphere.

CO2 Global Average

The globally averaged CO2 mole fraction in 2012 was 393.1±0.1 ppm. The mean annual increase from 2011 to 2012, 2.2 ppm, is greater than the increase from 2010 to 2011, the average growth rate for the 1990s (~1.5 ppm/yr) and the average growth rate for the past decade (~2.0 ppm/yr).

Global average abundances of the major, well-mixed, long-lived greenhouse gases – carbon dioxide, methane, nitrous oxide, CFC-12 and CFC-11 – from the NOAA global air sampling network are plotted since the beginning of 1979. These gases account for about 96% of the direct radiative forcing by long-lived greenhouse gases since 1750. The remaining 4% is contributed by an assortment of 15 minor halogenated gases including HCFC-22 and HFC-134a. Source: ESRL/NOAA

Methane (CH4) – THe Second Major Contributor

Methane contributes ~18% to radiative forcing by LLGHGs. Approximately 40% of methane is emitted into the atmosphere by natural sources (e.g., wetlands and termites), and about 60% comes from anthropogenic sources (e.g., ruminants, rice agriculture, fossil fuel exploitation, landfills and biomass burning). Atmospheric CH4 reached 260% of the pre-industrial level (~700 ppb) due to increased emissions from anthropogenic sources. Globally averaged CH4 reached a new high of 1819 ± 1 ppb in 2012, an increase of 6 ppb with respect to the previous year (Figure 4). The growth rate of CH4 decreased from ~13 ppb/yr during the early 1980s to near zero during 1999-2006. Since 2007, atmospheric CH4 has been increasing again due to increased emissions in the tropical and mid-latitude
Northern Hemisphere. The attribution of this increase to anthropogenic and natural sources is difficult because the current network is insufficient to characterize emissions by region and source process.

Nitrous oxide (N2O )

Nitrous oxide contributes ~6% to radiative forcing by LLGHGs. It is the third most important contributor to the combined forcing. N2O is emitted into the atmosphere from both natural (about 60%) and anthropogenic sources (approximately 40%), including oceans, soil, biomass burning, fertilizer use, and various industrial processes. The globally averaged N2O mole fraction in 2012 reached 325.1 ±0.1 ppb, which is 0.9 ppb above the previous year and 120% of the pre-industrial level (270 ppb). The annual increase from 2011 to 2012 is greater than the mean growth rate over the past 10 years (0.80 ppb/yr).

aggi_2013 RF
Radiative forcing, relative to 1750, of all the long-lived greenhouse gases. The NOAA Annual Greenhouse Gas Index (AGGI), which is indexed to 1 for the year 1990, is shown on the right axis.  Of the five long-lived greenhouse gases that contribute 96% to radiative climate forcing, CO2 and N2O are the only ones that continue to increase at a regular rate. Radiative forcing from CH4 increased from 2007 to 2012 after remaining nearly constant from 1999 to 2006. While the radiative forcing of the long-lived, well-mixed greenhouse gases increased 32% from 1990 to 2012 (by ~0.69 watts m-2), CO2 has accounted for nearly 80% of this increase (~0.55 watts m-2). Source: ESRL/NOAA

Recent Global CO2

  • August 2013:     393.11 ppm
  • August 2012:     389.82 ppm

Up-to-date weekly average CO2 at Mauna Loa

  • Week beginning on October 27, 2013:     394.20 ppm
  • Weekly value from 1 year ago:     391.32 ppm
  • Weekly value from 10 years ago:     373.39 ppm

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