[HN Gopher] Tropical Rainforest Index
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       Tropical Rainforest Index
        
       Author : infodocket
       Score  : 9 points
       Date   : 2021-07-23 19:44 UTC (3 hours ago)
        
 (HTM) web link (www.udel.edu)
 (TXT) w3m dump (www.udel.edu)
        
       | throwawaysea wrote:
       | The short version of this paper (https://www.cell.com/one-
       | earth/fulltext/S2590-3322(21)00344-...) describes this new index
       | as follows:
       | 
       | > Here, we built a spatially explicit tropical forest
       | vulnerability index (TFVI) based on observations of forest cover,
       | carbon, and water fluxes to identify areas where rainforests are
       | losing resilience to disturbance and are changing toward an
       | irreversible state, a "tipping point."
       | 
       | The extended version of the paper (https://www.cell.com/one-
       | earth/pdfExtended/S2590-3322(21)003...) has a lot more detail and
       | math, and the underlying model is described on page 999 (13 in
       | the PDF) under Equation 8. The model is implemented using the rlm
       | function in R (https://www.rdocumentation.org/packages/MASS/versi
       | ons/7.3-54...), which fits a linear regression model using
       | iterated re-weighted least squares (IWLS). The input and output
       | variables can be seen on page 1022 (35 in the PDF) in Table S1.
       | 
       | As an aside, I really dislike the increasing use of "tipping
       | points" in discussions around climate change. It seems so vague
       | and imprecise, and the claim of irreversibility seems hard to
       | establish. In the context of this paper, if you read the extended
       | version, it seems tipping point here is essentially long-term
       | loss of _biomass_ (not necessarily a climate-related outcome).
       | Additionally, rather than irreversibility, the model they use
       | predicts losses as a 1-month or 1-year lagged outcome based on
       | various input stressor variables. The magnitude of the output
       | index will need to be _interpreted_ to determine how significant
       | the negative outcome is (that is, the model does not actually
       | determine an irreversible  'tipping point'). Here's the relevant
       | text:
       | 
       | > The absolute magnitude of TFVI represents the risk of critical
       | transitions that would result in abrupt decreases (negative
       | values) or increases (positive values) of the response variable
       | given long-term trends in the stressors. The larger the absolute
       | value of TFVI, the greater the risk of a critical transition to
       | either higher or lower value of the ecosystem response.
        
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       (page generated 2021-07-23 23:01 UTC)