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Pablo Almaraz

@palmaraz.bsky.social

85 followers 150 following 12 posts

Ecology, oceanography, applied mathematics. MSc in Mathematics, PhD in Marine Sciences and Technologies. Leading the @robustecolab.bsky.social‬ at @icman-csic.bsky.social. Lab's website: https://robustecologies.github.io.

robustecologies.github.io.

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Pablo Almaraz @palmaraz.bsky.social · Jul 9

There we go...

Robust Ecologies Lab @robustecolab.bsky.social · Jun 11

🧵The RELab opens! We explore how diverse ecologies cope with fluctuations while maintaining long-term integrity in space and time. Our motto is: ‘Everything is moving’. Not interested in asymptotics: transient dynamics reigns everywhere, every time. A supertransient thread with an arrow of time:

Reposted by Pablo Almaraz

Robust Ecologies Lab @robustecolab.bsky.social · Jun 11

🧵The RELab opens! We explore how diverse ecologies cope with fluctuations while maintaining long-term integrity in space and time. Our motto is: ‘Everything is moving’. Not interested in asymptotics: transient dynamics reigns everywhere, every time. A supertransient thread with an arrow of time:

Reposted by Pablo Almaraz

Xavier Picó @xavierpico.bsky.social · Jun 26

Thanks @palmaraz.bsky.social for your seminar today, which was the last one of the season before the summer break at @ebdonana.bsky.social. A great example of how maths can help us understand complex ecological processes

Xavier Picó @xavierpico.bsky.social · Jun 24

Our next seminar (and the last of this season) on Thursday 26 June at 13:00 CET #EBDseminars @ebdonana.bsky.social

Youtube link: youtube.com/live/ECZeqi0...

Pablo Almaraz @palmaraz.bsky.social · Jun 26

Big thanks to you Xavier, and to all the people for attending and asking great questions! It's been great to be back at the EBD @ebdonana.bsky.social !

Pablo Almaraz @palmaraz.bsky.social · Apr 17

This took a bit of time to get published, but finally here it is! A new measure of structural stability for ecological applications. All the transient and asymptotic equilibria jointly play a fundamental role in the qualitative dynamics of Lotka-volterra systems: link.springer.com/article/10.1...

Structural stability of invasion graphs for Lotka–Volterra systems - Journal of Mathematical Biology

In this paper, we study in detail the structure of the global attractor for the Lotka–Volterra system with a Volterra–Lyapunov stable structural matrix. We consider the invasion graph as recently intr...

link.springer.com

Pablo Almaraz @palmaraz.bsky.social · Apr 12

This is an open-access, reproducible project, GuadalShiftR, github.com/palmaraz/Gua..., also in Zenodo, zenodo.org/records/1063.... Developed @ICMAN_CSIC, @ebdonana, @CSIC.

Pablo Almaraz @palmaraz.bsky.social · Apr 12

Our paper is published in the Special Issue ‘Non-equilibrium perspectives in biological conservation’ sciencedirect.com/journal/biol.... It emerged from a long-held intuition, and pushed forward
@ICMAN_CSIC by joining forces with @drAndyGreen @ebdonana

Best job in the world money can’t buy. Field work in Doñana, near Caracoles ranch. Author: Pablo Almaraz, CC BY 4.0

Pablo Almaraz @palmaraz.bsky.social · Apr 12

Our study thus provides an empirical example of a catastrophic bifurcation triggered by a tipping point in the dynamics of a threatened vertebrate community: this highlights the relevance of history and multi-stability in explaining current patterns in biological conservation.

The Eurasian teal (Anas crecca) was one of the most affected species in Doñana marshes after the Pinatubo-induced catastrophic bifurcation.

Pablo Almaraz @palmaraz.bsky.social · Apr 12

A stochastic cusp catastrophe model suggests that the persistence of cold and dry conditions in the wintering areas, and the warm and wet conditions in the breeding grounds, modulated local conditions and induced hysteresis through behavioral shifts to alternative wintering sites

Diagram depicting the three-dimensional representation of the stochastic cusp catastrophe model fitted to the major community trend, as a function of the stratospheric aerosol optical depth (bifurcation parameter) and flooding extension (asymmetry parameter). The fitted values plotted in the maximum-likelihood cusp equilibrium surface (in green) are depicted as gray circles.

Pablo Almaraz @palmaraz.bsky.social · Apr 12

And we uncover the likely cause behind this persistent regime shift: the explosion of Mt. Pinatubo in Philippines in 1991 triggered an anomalous, but transient period of cold and dry winters in southern Europe, a harsh environment for wintering migrating birds

June 15, 1991: Mt. Pinatubo, a stratovolcano in the Philippines, erupted. The height of the ash plume reached >40 km. More than 10 km3 of magma was ejected: this was a plinian/ultra plinian, cataclysmic, event (VEI 6). CC BY-SA 4.0

Climatologies of composite anomalies obtained from the V3 of the Twentieth Century Reanalysis Project (https://psl.noaa.gov/data/20thC_Rean/). The composite anomaly from 1978 to 2013, excluding the transient period 1992–1995, is shown for air temperature (A) and precipitation rate (C). The composite anomaly for the transient period, 1992–1995, is shown for air temperature (B) and precipitation rate (D). The seasonal period considered excludes the summer months.

Pablo Almaraz @palmaraz.bsky.social · Apr 12

We now show that both periods are equally stable dynamically. However, structural stability, as measured through a new metric, the Bayesian posterior probability of feasibility, declined: the community became more fragile through time

$Probability of dynamical stability and feasibility of the wintering waterfowl community in Doñana marshes (1978–2013). Figs. A) and B) show the distribution in the unit circle of the posterior eigenvalues of the Jacobian matrix (Eq. 5) of the LVR state-space model fitted to the pre-Pinatubo period (A, 1978–1992) and the post-Pinatubo period (B, 1995–2013). The probability of stability is the fraction of the eigenvalues (modulus) strictly smaller than 1 in the posterior distribution. MAP is the maximum a posteriori density, and 90 % HDI the highest density interval. Figs. C) and D) show the posterior histograms of the equilibrium abundances (N*) and the posterior averages of the carrying capacities for each waterfowl species (red dots) in the pre-Pinatubo period (C) and the post-Pinatubo period (D). The probability of feasibility for each period is the proportion of posterior estimated equilibrium abundance vectors in which the abundances are strictly positive for all species.$

Pablo Almaraz @palmaraz.bsky.social · Apr 12

In a previous paper (besjournals.onlinelibrary.wiley.com/doi/full/10....), we were intrigued by a regime shift to low fluctuating population levels in waterfowl community abundance starting in 1991. Even today, most species have not recovered their pre-1991 abundance levels!

Time series for wintering waterfowl species in Guadalquivir marshes, from 1973 to nowadays. Source: ICTS-RBD, CC BY-SA 4.0

Time series for wintering pooled Anatidae species in Guadalquivir marshes, from 1973 to nowadays. Source: ICTS-RBD, CC BY-SA 4.0

Pablo Almaraz @palmaraz.bsky.social · Apr 12

Doñana is an ever-changing ecosystem varying wildly in the extension of flooded surface, both within and among years, at all time scales. This is a key to its once-thriving biodiversity. Worryingly, this no longer seems to be the case (e.g., link.springer.com/article/10.1...)

Dramatic change in the flooding extension in the Guadalquivir marshes among two consecutive years. This is normal. Source: Copernicus, https://www.copernicus.eu/

Pablo Almaraz @palmaraz.bsky.social · Apr 12

📢!! Doñana wetlands are a @UNESCO World Heritage Site, currently under severe threats from anthropogenic pressures. In a recent paper we provide a clue to the dynamic and structural fragility of the 36-year waterbird community in the Guadalquivir marshes, doi.org/10.1016/j.bi...

Marsh horses (Caballo marismeño) feeding among Ranunculus peltatus in Marisma de Hinojos, Doñana National Park. This semi-wild horse is in danger of extinction. Author: Pablo Almaraz, CC BY 4.0

A Greater Flamingo (Phoenicopterus roseus) taking-off in Marismas de Hinojos, Doñana National Park. Author: Pablo Almaraz, CC BY 4.0