j.g. pausas' blog

This post complements the letter published today in the Science [doi] – A version of that letter is also available in Turkish here.

Turkey was hit hard by wildfires in 2021, with a record of about 203,000 ha burnt. Most of the area burnt was covered by Mediterranean Pinus brutia forests. Pinus brutia is not a fire-resistant trees, it dies after a fire; however, they have serotinous cones thus after fire the seeds are dispersed and new individuals recruit few months later. This forest also includes many shrubs able to resprout or germinate after fire. Thus natural regeneration was expected in most of the affected area. In fact, 4 months after fire, we already observed pine seedlings and many species resprouting [link]. To preserve this ecosystems, it is important to preserve their regeneration potential. Usually, quick postfire management is only needed if soil losses are likely; in those environments, soil losses typically occurs in only a small proportion of the landscape.

However, the Turkish government is cutting all dead trees (salvage logging). In many places, heavy machinery is being used and forest roads are being opened. In some cases, logging is followed by seeding or by terracing and new tree planting. That is, in some places they are transforming an ecosystem to an artificial afforestation. Thus the postfire management actions are more disturbing than the fire. And these postfire actions are taking place in both unprotected public forests and in conservation areas (e.g. Marmaris National Park).

It is worth remembering that standing dead trees have many ecological functions such as to reduce the impact of raindrops on the ground (i.e., reducing erosion), maintain some humidity, capture water from fogs, serve as perches for birds that bring seeds and contribute to the regeneration, and are habitat for many fauna (mainly invertebrates and some birds). And when dead trees fall down, they provide organic matter and nutrients to the soil. 

We urge the Turkish General Directorate of Forestry to stop degrading ecosystems and move toward more ecologically sustainable forest management.

All photos below were Pinus brutia forests.

Postfire salvage logging of burned trees in the Marmaris area

Examples of destroying potential natural postfire regeneration in Antayla, Turkey. Click the image to enlarge. Photos: link

References

[1] Tavsanoglu, Ç. & Pausas J.G: 2022. Turkish postfire action overlooks biodiversity. Science [doi | pdf | Turkish version]

[2] Marmaris postfire regeneration, jgpausas.blogs.uv.es/2021/12/05/

The role of large herbivores in explaining broad-scale ecological pattern has often been underestimated [1]. Plants have defenses against large herbivores (e.g., spines, high wood density [2]). And many continents had abundant large herbivores (megafauna) that were extinguished in Pleistocene (except in Africa). In a recent paper [3] we asked, to what extent the past distribution of extinct magafauna explains current geographical distribution of plant defense traits in the Neotropics (South & Central America). We fond that a significant proportion of the variance in the distribution of wood density, leaf size, stem spines, and leaf spines are explained by variable related to past megafauna (richness and body mass).

We defined 3 antiherbiomes in South America, that is, regions with characteristic plant defenses, environmental conditions, and Pleistocene megafauna, as follows: Small-Leaves-Thorny (SLT): thorny and small-leaved plants, in arid, cold and nutrient-rich ecosystems, containing numerous extinct and extant large grazers. Intermediate-Leaves-Woody (ILW): intermediate leaf sizes and levels of chemical defenses, and very high wood density, in moist and hot climates, and extremely nutrient-poor soils; and a high extinct megafauna richness, especially in relation to small browsers and mixed-feeders. Broad-Chemically-defended-Leaves (BCL): very large leaves with chemical defenses, mostly associated with moist climates and intermediate fertility soils, with few but large extinct megafauna species, especially browsers. Similar antiherbiomes can be observed in current Africa. These antiherbiomes represent one of the most striking broad-scale anachronisms in ecology.

We estimated that in South America, savannas occupied about 10 millions of Km² during the Pleistocene, ca. 63% of them were converted to forests (44% to moist forests, 19% to dry forests) after the megafauna extinction (biome shifts [4]), and ca. 37% remains as savanna (stable). This suggests that South America was a savanna-dominated continent, much more similar to Africa than today, and that a large proportion of South American forests are the result of megafauna extinctions.

Overall our results suggest that past (extinct) large herbivores explain an important proportion of the variability of current plant traits and community assemblies.

Fig. 3. Additional reconstructions of the Pleistocene Brazilian savannas from [5]. Artist: Júlia d’Oliveira

References

[1] Pausas JG & Bond WJ. 2019. Humboldt and the reinvention of nature. J. Ecol. 107: 1031-1037. [doi | jecol blog | jgp blog | pdf]

[2] Dantas V & Pausas JG. 2020. Megafauna biogeography explains plant functional trait variability in the tropics. Glob. Ecol. & Biogeogr. [doi | pdf | data:dryad | blog ]

[3] Dantas V., Pausas J.G. 2022. The legacy of Southern American extinct megafauna on plants and biomes. Nature Comm. 13: 129 [doi | pdf | data & codes] – New!

[4] [2] Pausas JG & Bond WJ. 2020. Alternative biome states in terrestrial ecosystems. Trends Plant Sci. 25: 250-263. [doi | sciencedirect | cell | pdf]

[5] Pansani et al. 2019. Isotopic paleoecology (δ13C, δ18O) of Late Quaternary megafauna from Mato Grosso do Sul and Bahia States, Brazil. Quat Sci Rev, 221, 105864.