Researchers from the Hebrew University disprove the common ecological concept that a wide variety of habitats contributes to the diversity of animal and plant species
What determines the number of species in an ecosystem and why are there more than ten million animals, plants and unicellular animals in nature? This question was defined in the last decade by the journal Science as one of the 25 most important scientific questions. For decades, the accepted ecological theory has been that the number of species that can exist in a certain area increases as the area includes more and more diverse habitats that differ from each other in environmental conditions, such as their height in relation to sea level and the amount of precipitation that falls in them. However, a new study recently published in the prestigious journal PNAS succeeds in disproving the old theory and presents surprising conclusions regarding the connection between the variety of environmental conditions and the variety of species in nature.
The old ecological concept was put to the test by research students Omri Alosh and Michael Kaluzhani under the guidance of Prof. Ronan Kadmon from the Institute of Life Sciences at the Hebrew University, in collaboration with researchers from the University of Granada in Spain. The researchers developed a mathematical model that describes the development of an ecosystem consisting of specifications of different species and then tested the model's predictions through empirical analysis of dozens of databases of plant and animal species from around the world.
Both the theoretical results of the model and the data from the field supported the hypothesis that diversity in habitat conditions can actually increase the extinction rates of species and thereby decrease the number of species that can exist in the system. For example, the analysis of the diversity of hundreds of nesting bird species in Catalonia revealed that precisely in areas where the environmental conditions were more diverse, more bird species became extinct over the years than in homogeneous areas. According to research student Michael Kaluzheni, "the explanation for the research findings is that in a diverse environment in terms of habitat conditions, there is less space and resources suitable for each of the species, and therefore the species become more vulnerable to local extinctions. Hence, over-diversification in habitat conditions may actually lead to a decrease in the number of species."
"The findings are of great importance for nature conservation since the accepted concept gives priority to preserving areas with diverse environmental conditions and even encourages taking artificial measures to increase the diversity of habitats" explains Prof. Kadmon. "The results of the study show that such an approach can lead to the opposite of the desired results, especially when it comes to areas that are limited in scope, a typical situation for many nature reserves in Israel and around the world." According to Prof. Kadmon,
"In our time, ecosystems and the species that make them up are under increasing pressure from human activity. Under such conditions, the ability to intelligently manage open spaces and nature reserves is of great importance. I hope that the research will provide important insights to policy makers and scientists when they come to decide on areas that are suitable for conservation and actions that should be taken in such areas."
The research was conducted with funding from the National Science Foundation and the Ministry of Science and Technology.
7 תגובות
to collect, to collect (other), to doubt, and legal
Asaf,
Such a model can have one parameter for area and another parameter for the degree of diversity. The researchers showed that in their model, high diversity reduces the number of species relative to moderate diversity, under a very large range of areas.
Regarding "what is the minimum area so that the habitats do not lose their vitality" - this is a very difficult question. For this you need to characterize very precisely the degree of stability of the conditions in the habitat. But without a doubt this is an important research direction.
The above study is essentially a basic study that provides theoretical and empirical evidence for an unknown mechanism. In order to become practical there is no doubt that several more steps must be taken.
collect (the other),
The study does not refer to human activity at all. Why do you assume that there is no "strain on habitats" without human activity? Is there no competition in nature for limited resources? If you compare similar areas in different size conditions, won't you find more species in the larger area?
skeptic,
right. Let's destroy those who produce tomorrow's drugs, tomorrow's biotechnological methods and our understanding of ourselves in a broad context. And along the way, we'll screw up our legacy. I am in favor.
Yigal C,
A habitat can house one or more populations. But why assume that if a population went extinct, the habitat was not good? What about competition with other species? What about particularly bad years or finding partners (as with Benjamin)? Is the number of species in an ecosystem derived one to one, linearly, from the number of habitats?
The result makes sense. The more species there are
Life hunting insects (for example) on a limited area,
The chance of two mature individuals finding it is small
This for reproductive purposes - compared to a situation where there is only one species
holding the same area.
If ten species are hunted in the same area, a number
The mature individuals of each species may not be sufficient
to establish new generations - and all ten species will become extinct.
The problem probably lies in the definition of the term "habitat". Is a habitat a niche capable of sustaining a certain population? For what period and can the conditions change and in what way? Obviously if the population did not survive, then the habitat was not suitable for it for some reason and perhaps it does not deserve to be called a habitat. In any case, the conclusions expressed in the article are problematic.
Safkan,
Your view is very narrow, there are countless reasons why a person should live in harmony with nature and not destroy it, some of the reasons are technologies such as a new source of medicine, some are hedonistic such as a place to travel and some are unknown such as harming bees without which humanity will die.
But in my opinion the most important reason is moral and without morality we are all doomed.
There is no need to leave in the wild species that deserve to be extinct due to their unfitness to survive.
Nature is not a zoo for the purposes of entertainment or to satisfy the delicate soul of animal lovers.
I don't think the conclusion of the study is correct. He talks about the rate of extinction of animals at a moment of hunger for the habitats, for example as a result of human activity. There is no doubt that certain habitats are more sensitive to changes than other habitats, but there is no discussion at all about the total number of species that were in the habitats to begin with. In my opinion, the research only reinforces the need to preserve unique habitats since the animals are more sensitive to damage to their environment.
I don't know how to "develop a mathematical model" for an area with a variety of habitats
But it is clear that there will be huge differences between a small area and a large area,
Because the wider and larger the habitat, the more chances the species living in it have
good existence,
It is clear that when there is a density of habitats in a small area
There will be greater competition between species within each habitat
As well as the competition between species in neighboring habitats.
I don't know the environmental conditions in Catalonia but if it exists there
A certain habitat over a large area and surrounding habitats in the areas
The proposal will be accepted as in the research conclusions,
In contrast, if the whole country (Israel) is treated as one territory
After all, the greater the variety of habitats, the greater the number of species,
So the problem in Israel is the small area and not a large variety of habitats
and the fact that the habitats are too small to allow vital populations,
There are no corridors and similar habitats and this is (again) a factor
for lack of vitality,
In my opinion, it would have been appropriate for the researchers to define the size of the area being tested
and how many and what variety of habitats in it,
What is the "minimum" size of a tested area for the habitats in it
will not lose their vitality,
It is possible that "the encouragement of taking artificial measures to increase the diversity of the habitats"
is not always the right activity,
But in our tiny country there are cases where there is no choice and sometimes
When you want to restore a habitat and restore it, it is necessary to create artificial conditions
which do not always correspond to the conditions affected,
And again what is missing for the research to be a basis for action
They are orders of magnitude.