[ad_1]
When standing directly in the forest around Yading Village (Nyidên), China, the number of closely related species can not be perceived as exceptionally high. However, the nature of the forest changes rapidly when you go up, down or in another valley. Credit: Adrien Favre / Senckenberg
Biodiversity is one of the most valuable resources on Earth. However, in most countries of the world, scientists have little idea of what diversity is. Researchers from the German Center for Integrative Research on Biodiversity (iDiv) and the Martin Luther University of Halle-Wittenberg (MLU) have now constructed from a scattered data map of the world of biodiversity indicating the number of # 39; species of trees. With the new map, researchers were able to deduce what conditions the global distribution of tree species richness. The climate plays a central role. However, the number of species that one can find in a given region also depends on the spatial scale of the observation, the researchers report in the newspaper. Nature Ecology and Evolution. The new approach could help improve global conservation.
Around the world, biodiversity is changing dramatically and its protection has become one of the biggest challenges facing humankind. Researchers still know very little about biodiversity in some places, while others are poor and in areas with the highest biodiversity. In addition, the reasons why some areas are richer in species than others are often unclear: what role do environmental factors such as climate play and how important are historical factors such as periods of past ice for the biodiversity we observe today? Current knowledge is based on scattered local surveys and is flawed, especially in tropical regions, where biodiversity may be particularly high. However, it is simply impossible to fill all the gaps by exhaustively surveying the whole planet.
Satellite imagery can fill some gaps in the data, for example when collecting information on forest cover, but these techniques have their limitations. "We must not only count the trees, we must also identify their species," says Dr. Petr Keil, lead author of the new study. "In the tropics, we find hundreds of different tree species on a single hectare.We can only identify them on the spot.Therefore, most areas have not done the same." 39, subject of a biodiversity survey – and will probably never be. " Keil and the co-author, Professor Jonathan Chase, are scientists at the German Center for Integrative Research on Biodiversity (iDiv) and Martin Luther University in Halle-Wittenberg.
The mountains of Harenna Forest in Ethiopia are another example of an area with a wide variety of forest types and, therefore, a great regional diversity. Credit: Laica ac UK, CC BY-SA 0.2
Despite uneven data, Keil and Chase wanted to create a map of the world's wealth of tree species. At first, they compiled more than 1,000 lists of tree species. These came either from small forest plots that had been studied in previous studies or whole countries. We know which tree species are found in most countries, but not exactly where, and it is often difficult to know if specific species are rare or common. In order to calculate the number of tree species for the vast open spaces of the map, the researchers developed a statistical model. The trick is that the model combines the scattered information available on the plots studied with information at the country level, and also incorporates data built on environmental factors such as climate. The result is a complete map of biodiversity in all forest areas of the world.
"It was like a 1000-piece puzzle for which we had only a few pieces, and we did not even know what the whole situation was," says Jonathan Chase. "Thanks to our approach, we were able to calculate the missing pieces and assemble the puzzle." With the help of the new method, researchers can calculate the number of tree species for areas of different sizes – a nature reserve, a country or an entire continent. This allowed them to study the underlying causes of variation in tree diversity on Earth. Their analysis revealed that climate was the most important factor. the largest number of tree species is found in the hot and humid tropics. Nevertheless, the number of tree species also varies according to the regions enjoying the same climate, sometimes in quite significant proportions. In southern China, for example, researchers find much greater diversity than in other regions with a similar climate.
It is important to note, however, that the amount of additional diversity in countries such as China depends on the viewpoint of the observer. "If you are in a forest and you count the number of species around you, you may not even notice the difference between China and other similar regions in terms of climate. when you move from one site to another and you add the species observed sites, the difference really appears, "says Jonathan Chase.
Upper Figure: First world map of species richness of trees, produced by the new model. It illustrates the number of tree species that can be expected on areas of one hectare. The largest number of tree species (orange to yellow) can be found in the hot and humid tropics. The remaining white spaces are unavoidable areas. Bottom figure: When tree diversity is observed at the scale of large areas, the image changes. A particularly high number of species (orange to yellow) can now be observed in mountainous areas such as southern China, Mexico or the Ethiopian highlands, all of which have high beta diversity. Credit: Petr Keil and Jonathan Chase
This disparity between adjacent areas is called beta diversity. In a larger region, this leads to high total diversity. Keil and Chase have shown in their analysis that this measure of diversity is particularly high in the dry (and non-humid) tropics, particularly in mountainous areas such as southern China, Mexico or the Ethiopian highlands. One reason for this high beta diversity could be due to events in the geologic past, such as ice ages. "During the last glaciation, trees could only survive in the mountain valleys and different populations were isolated from each other," says Petr Keil. "If you find yourself in one of these valleys today, you will see an average number of tree species, but if you go up on the ridge and go down to the next valley, you will find different species of trees and still others in the nearby valley. "
Keil and Chase are primarily interested in understanding how biodiversity is distributed on the planet and what factors are driving it. But their model can also be useful for developing conservation strategies, especially in forests where tree diversity has not been heavily influenced by humans. For example, in the case of the Chinese mountains, protecting a single valley is not enough; it is the diversity of valleys that gives this region its high biological value. "In order to truly understand and protect biodiversity, we need to look at both the local and regional scales," said Keil. "In other words, we need both the perspective of a naturalist in a forest and the overall vision of a country.Our approach allows it now."
Explore further:
Animals and fungi improve forest performance
More information:
Petr Keil et al., Global models and tree diversity factors integrated into a space grain continuum, Nature Ecology & Evolution (2019). DOI: 10.1038 / s41559-019-0799-0
[ad_2]
Source link