Climate Change Threatens Coexistence within Communities of Mediterranean Forested Wetlands

Abstract

The Mediterranean region is one of the hot spots of climate change. This study aims at understanding what are the conditions sustaining tree diversity in Mediterranean wet forests under future scenarios of altered hydrological regimes. The core of the work is a quantitative, dynamic model describing the coexistence of different Mediterranean tree species, typical of arid or semi-arid wetlands. Two kind of species, i.e. Hygrophilous (drought sensitive, flood resistant) and Non-hygrophilous (drought resistant, flood sensitive), are broadly defined according to the distinct adaptive strategies of trees against water stress of summer drought and winter flooding. We argue that at intermediate levels of water supply the dual role of water (resource and stress) results in the coexistence of the two kind of species. A bifurcation analysis allows us to assess the effects of climate change on the coexistence of the two species in order to highlight the impacts of predicted climate scenarios on tree diversity. Specifically, the model has been applied to Mediterranean coastal swamp forests of Central Italy located at Castelporziano Estate and Circeo National Park. Our results show that there are distinct rainfall thresholds beyond which stable coexistence becomes impossible. Regional climatic projections show that the lower rainfall threshold may be approached or crossed during the XXI century, calling for an urgent adaptation and mitigation response to prevent biodiversity losses.

Coexistence trend contingent to Mediterranean oaks with different leaf habits

“…Here we give a brief overview of the model, which background is useful to understand the mechanism allowing for a stable coexistence. It was presented in detail in (Di Paola et al., ), and we refer the interested reader to our previous paper for the stability analysis and any further details.…”

“…It was presented in detail in (Di Paola et al, 2012), and we refer the interested reader to our previous paper for the stability analysis and any further details.…”

“…In a previous work (Di Paola, Valentini, & Paparella, ) we developed a mathematical model to represent the co‐occurrence of sclerophyllous evergreen oaks ( Q. ilex and Q. suber ) and deciduous oaks (dominated by a typical endemism of Q. cerris and Q. frainetto , as well as Q. robur ) in two sites of Tyrrhenian plain forests (western coast of Italy), where the abundance of edaphic water, despite the warm Mediterranean climate, allows the co‐occurrence of these species.…”

Integrating Homo sapiens into ecological models: Imperatives of climate change

“…We do not know exactly where the bifurcation value(s) lies, but scientists are becoming increasingly adept at modelling the physical processes connected with climate change (Mora et al, 2013), and mathematical biologists (and many others) are able to provide wellinformed estimates of species survival under various scenarios (Gilman et al, 2010;Di Paola et al, 2012). At just 2 8C of warming, significant negative impacts are anticipated (Elkin et al, 2013) and some regions will likely experience an average warming of much more than 2 8C (Corlett, 2012).…”

“…This approach is fine as long as the anticipated change is not too drastic, and simply adapting to the altered climate is sufficient. Unfortunately, we have reached a point where catastrophic bifurcations are entirely possible (Boulton et al, 2013;Budzianowski, 2013;Di Paola et al, 2012;Ashwin et al, 2012;Kwadijk et al, 2010). A recent report (Schwartz and Randall, 2003;Shearer, 2005) examined threats to National U.S. Security posed by climate change through disruptions of food, water, or fuel: ''[o]cean, land, and atmosphere scientists at some of the world's most prestigious organizations have uncovered new evidence over the past decade suggesting that the plausibility of severe and rapid climate change is higher than most of the scientific community and perhaps all of the political community is prepared for.''…”