Warning! We’re depressing biodiveristy below safe levels.

Summary: We have been shaping Earth’s biosphere for millennia, but increasing population and technology have exponentially increased our impacts. Research has begun to quantify our net impact and establish levels beyond which the damage becomes serious or terminal. Here’s the latest study. This problem will grow worse as population and incomes grow during the next several decades.

Track human impacts on Earth, setting safe planetary boundaries

By F. Pharand-Deschênes /Globaïa.
By F. Pharand-Deschênes /Globaïa. By F. Pharand-Deschênes /Globaïa. Click to enlarge.

The latest study warning us is “Has land use pushed terrestrial biodiversity beyond the planetary boundary? A global assessment.” — by Tim Newbold et al in Science, 15 July 2016. Gated; here’s the abstract…

“Land use and related pressures have reduced local terrestrial biodiversity, but it is unclear how the magnitude of change relates to the recently proposed planetary boundary (“safe limit”). We estimate that land use and related pressures have already reduced local biodiversity intactness — the average proportion of natural biodiversity remaining in local ecosystems — beyond its recently proposed planetary boundary across 58.1% of the world’s land surface, where 71.4% of the human population live. Biodiversity intactness within most biomes (especially grassland biomes), most biodiversity hotspots, and even some wilderness areas is inferred to be beyond the boundary. Such widespread transgression of safe limits suggests that biodiversity loss, if unchecked, will undermine efforts toward long-term sustainable development.”

Excerpt

“Land use and related pressures have been the main drivers of terrestrial biodiversity change and are increasing. Biodiversity has already experienced widespread large net losses, potentially compromising its contribution to resilient provision of ecosystem functions and services, such as biomass production and pollination, that underpin human well-being.

“Species-removal experiments suggest that loss of ecosystem function accelerates with ongoing species loss beyond which human intervention is needed to ensure adequate local ecosystem function (8, 9). The loss of 20% of species — which affects ecosystem productivity as strongly as other direct drivers — is one possible threshold, but it is unclear by which mechanism species richness affects ecosystem function and whether there are direct effects or only effects on resilience of function.

“Whereas this proposed safe limit comes from studies of local ecosystem health, the Planetary Boundaries framework {see their website} considers longer-term maintenance of function over much larger (biome to global) scales. At these temporal and spatial scales, the maintenance of function depends on functional diversity — the ranges and abundances of the functional traits of the species present. Because direct functional trait data are lacking, the Biodiversity Intactness Index [BII; the average abundance of originally present species across a broad range of species, relative to abundance in an undisturbed habitat] is suggested as the best metric. The safe limit is placed at a precautionary 10% reduction in BII, but it might be as high as a 70% reduction.

“…Given the possibly severe consequences of transgressing safe biodiversity limits, global assessments of relevant metrics are needed urgently. Data limitations have hampered efforts to date; BII has so far only been estimated, from expert opinion, for seven southern African countries.

“…The Sustainable Development Goals adopted in September 2015 aim to improve being while protecting, restoring, and sustainably using terrestrial ecosystems. Our results highlight the magnitude of the challenge. Exploitation of terrestrial systems has been vital for human development throughout history, but the cost to biosphere integrity has been high. Slowing or reversing the global loss of local biodiversity will require preserving the remaining areas of natural (primary) vegetation and, so far as possible, restoring human-used lands to natural (secondary) vegetation. Such an outcome would be beneficial for biodiversity, ecosystems, and—at least in the long term — human well-being.”

Terrestrial area and human population at different levels of BII

Population and area occupied

Legend
Values for Biodiversity Intactness Index.
  • Biodiversity intactness increases from bottom left to top right (color for each level of BII in box at right).
  • The dashed black line shows the position of the planetary boundary: only areas to the right and human population above this line (shaded green and blue) are within the proposed safe operating space.
  • If human population were distributed randomly with respect to BII, the corners of the boxes would align with the dashed gray line; the extent to which the corners lie above this line indicates the strength of the bias in human populations toward less intact areas.

Conclusion

We have to learn to respond to multiple threats running over different time horizons. Some of the greatest and most certain risks — like the relentless destruction of species (symptom of our wrecking the biosphere) — received too little attention compared to those threats whose solutions offer political gains (e.g., the taxes and regulations to fight climate change). It’s no way to run a world.

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2 thoughts on “Warning! We’re depressing biodiveristy below safe levels.

  1. Very interesting ! As a planet we really need to take action, although mass extinctions have been common throughout time, our current loss of biodiversity is definitely not common place !

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