Corresponding author: Merja Elo ( merja.t.elo@jyu.fi ) Academic editor: Stephane Boyer
© 2017 Merja Elo, Tuomas Haapalehto, Santtu Kareksela, Janne Kotiaho.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Elo M, Haapalehto T, Kareksela S, Kotiaho JS (2017) What does the recovery debt really measure? Rethinking Ecology 2: 41-45. https://doi.org/10.3897/rethinkingecology.2.21840
|
Recently,
An undesired change in biodiversity, ecosystem functions or services due to anthropogenic disturbance is customarily called degradation. Magnitude of degradation can be estimated as the difference between the current state of the ecosystem and its undisturbed natural state (
A schematic figure describing how degradation and the recovery debt are estimated in relation to undisturbed and disturbed ecosystem states. a) The difference between diversity/ecosystem function and the magnitude of degradation relative to an undisturbed natural state reference. While diversity/ecosystem function can decrease or increase due to anthropogenic disturbance relative to the undisturbed reference state (Xr, grey dashed line), both lower and higher values than the undisturbed reference state can be considered degradation. It is worth noting, however, that while increase and decrease are neutral descriptors of change, by labelling any deviation from the natural state as degradation we are making a value statement that such change is undesired. b) The influence of the inverse-transformation on the diversity/ecosystem function values and recovery debt. The recovery debt sensu
While an effort to estimate the lost ecosystem diversity, functions and services due to delayed recovery is welcome, the significance of the concept is not as intuitive as it first appears. In particular, from the perspective of biodiversity per se the meaning of the concept is difficult to perceive. In essence, the recovery debt for diversity can be understood as the absolute number of lost diversity years (RD), or as an average diversity which was absent every year during the recovery process (RDt). Compared to the behaviour of the customary measure of the magnitude of degradation, which declines to zero during complete recovery, the absolute recovery debt (RD) increases until the diversity has reached the reference level and persists unchanged thereafter, while the recovery debt per annum (RDt) asymptotically approaches zero but only in infinity. In such a case, and still focusing exclusively on the diversity per se, we do not understand how the recovery debt values that persist after the complete recovery of the ecosystem improve our understanding of the magnitude of degradation of the ecosystem. Therefore, we feel that further clarification of the meaning and importance of the concept is needed before the concept is adopted to be used for diversity.
Nevertheless, as Moreno-Mateos et al. state, “… shortfalls in biodiversity and ecosystem functionality will affect the quantity and quality of ecosystem services provided by the recovering ecosystems”. Thus, the recovery debt potentially gains its meaning through the perspective of lost anthropogenic benefits. In particular, this might be the case for variables measured per annum basis, such as carbon sequestration, recovery debt being the amount of carbon remaining in the atmosphere due to the lost sequestration during the recovery process.
Unfortunately, the way the recovery debt is operationalised makes the measure ambiguous also in terms of the ecosystem services. In the methods, Moreno-Mateos et al. state that there were many cases, apparently nearly half of the data, where the starting values of the measured response variables for the recovering ecosystems were greater than those in the reference ecosystems and continue: “in these cases, we assumed that response values above the reference value represent negative effects, and thus [such response values] were inverse-transformed using the formula Zs,e = Xr*(Xr/Xs,e)”. This calculation transforms the values that are greater than the reference to become smaller than the reference (Fig.
What the recovery debt really quantifies is the interim deviation rather than reduction of biodiversity and ecosystem functions from undisturbed state. These two are obviously very different things. The ambiguity seems to be reflected in the way the recovery debt values are constantly referred as ‘reductions’ or ‘deficits’ of biodiversity and functions. However, the reason why all the data appear as reductions is the inverse-transformation. Therefore, the contrast to previous studies showing that α-diversity does not change through time (
As such the inverse-transformation relative to the undisturbed natural reference state has an interesting underlying assumption: every focal location has its own characteristic diversity and ecosystem functions, and any deviation from this is degradation – be it increased or reduced diversity or function (Fig.
ME and JSK conceived the ideas and drafted the manuscript. TH and SK critically commented on the manuscript and developed the ideas further.
Authors | Contribution | ACI |
---|---|---|
ME | 0.40 | 2.00 |
JSK | 0.40 | 2.00 |
TH | 0.10 | 0.33 |
SK | 0.10 | 0.33 |
We are thankful for Kone Foundation (for ME) for funding this research.