One black mangrove (Avicennia germinans) recently established grows in the middle of a brackish swamp north of St. Augustine, Florida, near the northern border of this cold-sensitive tropical tree. Mangroves are expanding in northern Florida as the episodes of intense cold become rarer. Photograph: Kyle C. Cavanaugh (Landsat Satellite Sees Florida Mangroves Migrate North)
I evoked in a previous article (Ecosistemas terciarios desaparecidos), the presence of mangroves on the southern coast of the Iberian peninsula at the end of the Tertiary and early Quaternary, documented by the discovery of extraordinarily well preserved fossils whose study is still underway (Hallados fósiles de manglares de hace 2,5 millones de años en Cuevas). Based on this I imagined, in another more recent article (Rumbo al Plioceno), as in the future more or less distant the Romería del Rocío possibly have to progress in boats between the roots of the mangroves. In writing this article, however, I was not aware that the possibility of seeing a mangrove grow on our coast may not be as far as I expected...
Current distribution of Avicennia germinans
As you can see in the previous map, the black mangrove (Avicennia germinans) reaches in North America the eastern shores of Florida. The northern boundary of its distribution does not seem to be so marked by average annual temperatures or rainfall, but by the fact that there are cold days when the temperature falls below -4 ° C. Below this temperature, black mangrove seedlings do not survive. On the other hand, a relatively recent study [1] has shown that global warming has led to the development of the mangrove swamp in the north since the 1980s, where the tree colonizes coastal areas.
As you are intelligent and have agile minds, you have surely noticed seeing the map of distribution of this species that the north of Florida is situated at about the same latitude as the Canaries. And as you well know, the Gulf Stream flows southward off the coast of North America, bringing cold waters from the north, and rising northward off the coasts of Africa and Europe. In addition, there are many areas of southern Spain, where temperatures do not drop below 0 degrees. Huelva, for example, is often the city of Spain with the highest minimum temperature. The cold ever in this city was -5.8 degrees and was achieved in 1938. Later, it only reached that limit of -4ºC in 1954. The big question, you guessed it, is this: could the black mangrove survive in southern Spain? As far as I know, no one happened to try to plant this species in our country, but seeing that the climatic limitation marks the limit of its distribution in Florida, I wonder if perhaps the experiment is worthwhile, although only to clear the doubts. In the worst case we would have a small mangrove swamp on our coast...
Potencial distribution of Avicennia germinans suposing that this species is able to survive in zones where frost is exceptional. Author: Joâo Ferro.
| Avicennia | Family: Acanthaceae | Order: Lamiales | |
Shrubs or trees, maritime. Branches terete, sometimes 4-ridged when young. Leaves opposite. Inflorescences small spikes or capitula; bracts and bractlets ovate, shorter than calyx, persistent. Flowers small, opposite, sessile. Calyx cup-shaped, deeply 5-lobed; lobes overlapping, persistent. Corolla nearly actinomorphic, campanulate, shortly inserted on an inconspicuous disc; lobes 4 or 5, upper lobe often broader than others. Stamens 4, adnate to apical part of corolla tube. Ovary imperfectly 4-locular, with a free central winged placenta; ovules pendulous. Capsules subtended by persistent calyx, dehiscent into 2 leathery valves. Description: Flora of China | |||
The presence of this genus on the European continent and in the Mediterranean is documented until the beginning of the Quaternary. Apparently the mangroves survived longer in the eastern Mediterranean basin, disappearing less than 2 million years ago around the Black Sea.
Latest records of Avicennia mangroves in the Mediterranean [2]
I did not live in Madrid, far from the sea and not have a holiday in very favorable areas, I do not think I would hesitate to try. The region of Huelva seems a priori to be the most favorable, but I have to admit that I do not know this region very well. Can you imagine how extraordinary it would be to have a small mangrove swamp on our coast? Not only for the curiosity but also for the multiple benefits that this type of ecosystem brings where it develops. Everyone probably knows that the mangroves are authentic nurseries for many species of fish. There is no doubt in my mind that such an initiative would quickly come to an end, with initial reluctance, the unconditional support of many people. Yes, the idea is launched. I hope that in this country people are even more insane than those who write these lines...
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[1] Cavanaugh K. C. et al. (2014) / Poleward expansion of mangroves is a threshold response to decreased frequency of extreme cold events / PNAS, Vol. 111(2), pp. 723–727 | |
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[2] Biltekin, Demet. (2010) / Vegetation and Climate of North Anatolian and North Aegean Region Since 7 Ma According to Pollen AnalysisTésis / Tésis / Université Claude Bernard – Lyon 1 & Université Technique d'Istanbul | |
Author: Adrián Rodríguez
Translation: João Ferro
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