MA: Humans are Changing Ecosystems Rapidly

It is very difficult to emotionally absorb what we are doing to our world. Some 10-30% of mammal, bird, and amphibian species are currently threatened with extinction, the Millennium Ecosystem Assessment (MA) and pretty much every other source have been telling us for years. Our work is to find ways to hear what is being said in reports like the MA, to really listen, and then to find ways to move beyond the paralysis of fear and guilt to do what we need to do.

Scientists credit the 1950s as the beginning of the 6th mass extinction since complex life began. National Geographic addresses this topic in The Fragile Web: “The sixth extinction is not happening because of some external force. It is happening because of us, Homo sapiens.”

You may wish to download or purchase Millennium Ecosystem Assessment Synthesis Report or other reports yourself. I’ve excerpted some of the report below, but you have to go to the report to see figure 3 to see the Conversion of Terrestrial Biomes. “Biome is the largest unit of ecological classification that is convenient to recognize below the entire globe, such as temperate broadleaf forests or montane grasslands.”

Notes: Mangrove forests are important areas of biodiversity. They also protect areas from storms: the 2004 tsunami inflicted less damage on areas with intact mangrove forests; similarly, the destruction of wetlands has led to years of predictions that New Orleans would be more vulnerable to hurricanes. Mangrove forests are being destroyed in order to create 5- year shrimp farms or for development. According to Walter Reid, director of the Millennium Ecosystem Assessment, even over the lifetime of the shrimp farms, conversion may not be good economic value if ecosystem services are considered.

The concentration of atmospheric carbon is now 380 parts per million, and is on track to reach 400 ppm by 2015.

From Millennium Ecosystem Assessment Synthesis Report:

Finding #1: Over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.

The structure and functioning of the world’s ecosystems changed more rapidly in the second half of the twentieth century than at any time in human history.

_ More land was converted to cropland since 1945 than in the eighteenth and nineteenth centuries combined. Cultivated systems (areas where at least 30% of the landscape is in croplands, shifting cultivation, confined livestock production, or freshwater aquaculture) now cover one quarter of Earth’s terrestrial surface.
_ Approximately 20% of the world’s coral reefs were lost and an additional 20% degraded in the last several decades of the twentieth century, and approximately 35% of mangrove area was lost during this time.
_ The amount of water impounded behind dams quadrupled since 1960, and three to six times as much water is held in reservoirs as in natural rivers. Water withdrawals from rivers and lakes doubled since 1960; most water use (70% worldwide) is for agriculture.
_ Since 1960, flows of reactive (biologically available) nitrogen in terrestrial ecosystems have doubled, and flows of phosphorus have tripled. More than half of all the synthetic nitrogen fertilizer, which was first manufactured in 1913, ever used on the planet has been used since 1985.
_ Since 1750, the atmospheric concentration of carbon dioxide has increased by about 32% (from about 280 to 376 parts per million in 2003), primarily due to the combustion of fossil fuels and land use changes. Approximately 60% of that increase (60 parts per million) has taken place since 1959.

Humans are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity.

_ More than two thirds of the area of 2 of the world’s 14 major terrestrial biomes and more than half of the area of four other biomes had been converted by 1990, primarily to agriculture. (See Figure 3.)
_ Across a range of taxonomic groups, either the population size or range or both of the majority of species is currently declining.
_ The distribution of species on Earth is becoming more homogenous; in other words, the set of species in any one region of the world is becoming more similar to the set in other regions primarily as a result of introductions of species, both intentionally and inadvertently in association with increased travel and shipping.
_ The number of species on the planet is declining. Over the past few hundred years, humans have increased the species extinction rate by as much as 1,000 times over background rates typical over the planet’s history (medium certainty). Some 10-30% of mammal, bird, and amphibian species are currently threatened with extinction (medium to high certainty). Freshwater ecosystems tend to have the highest proportion of species threatened with extinction.
_ Genetic diversity has declined globally, particularly among cultivated species.

Most changes to ecosystems have been made to meet a dramatic growth in the demand for food, water, timber, fiber, and fuel.

[M]ost ecosystem changes were the direct or indirect result of changes made to meet growing demands for ecosystem services, and in particular growing demands for food, water, timber, fiber, and fuel (fuelwood and hydropower). Between 1960 and 2000, the demand for ecosystem services grew significantly as world population doubled to 6 billion people and the global economy increased more than sixfold. To meet this demand, food production increased by roughly two-and-a-half times, water use doubled, wood harvests for pulp and paper production tripled, installed hydropower capacity doubled, and timber production increased by more than half.

Update: Conversion of Terrestrial Biomes is posted on the web

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