This article comes from WeChat public account: Jizhi Club (ID: swarma_org) , author: Guo Ruidong
Introduction: Today’s (March 3) is the theme of World Wildlife Day, this year Is “ Maintain all life on Earth “, including maintaining all the species of wildlife that make up biodiversity. In ecology, we usually use biodiversity to describe the degree of diversity in nature. Biodiversity has multiple levels of value, of which economic value is one that is easier to quantify. Economic value can directly guide the balancing and formulation of environmental protection policies. A February review paper by Science Advance discusses this topic in detail about the relationship between biodiversity and its economic value.
Conflicts between humans and nature continue to escalate
The 2020 United Nations Conference on Biological Diversity will be held in Kunming in October. The theme of the conference is “ Ecological Civilization: Building a Community of Earth’s Life “, and some commented that this will be a vital Moment, it determines the sustainable development of the world in the next decadeTowards. At present, in the face of a new coronavirus epidemic that is transmitted by wild animals, some legislative scholars have proposed “ecological killing” strategies for protecting species. We cannot help asking why people’s judgments on the value of biodiversity are so divided.
From climate warming, El Niño to globalization of transportation, from population growth to accelerated industrialization and urbanization, from Brazilian Amazon forest fires to natural fires in Australia, to this year’s new coronavirus outbreak, and locust plagues in Asia and Africa ——We are experiencing the personal pain brought about by the escalating disputes between man and nature. Ecosystem degradation, species extinction, and loss of biodiversity will have consequences for human society. These issues need to be considered at the core of sustainable development.
However, due to the overlapping of wildlife and human activities, human and animal health risks, the demand for food production, and control of pests and invasive species, many species have repeatedly stood on the “opposite side” with human social development. Contradictory and confusing. Conflicts among multiple values are increasingly emerging, and people are struggling to play a difficult game between seeking survival and development and protecting nature.
Undoubtedly, ecosystems have service functions such as resource supply support, material and climate regulation, and cultural spirit. The normal driving of this overall service function is a system characterized by its biodiversity. The structure is supported. How to bridge the two complex giant systems of nature and human beings, couple social demands with the laws of economic development and the laws of natural operation, and allow researchers, citizens and decision-makers to communicate and cooperate with each other. The intrinsic relationship between economic value, to achieve a truly effective trade-off (trade-off)
Waterfall model of biodiversity value
How much is biodiversity worth-should this account be calculated like this? According to the proposed framework, when discussing the economic value of biodiversity, it is examined step by step. First, it examines the functions of biodiversity itself, such as maintaining the stability of the ecosystem and promoting the redundancy of the ecosystem in the face of disturbances. I will then discuss what kind of services these functions can provide in economic activities, such as fish schools providing food for humans, and forests to prevent soil loss; finally, evaluate how the value of these economic services changes with the diversity of ecosystems .
Figure 1: A model for understanding the economic value of ecological diversity, a paper from Potschin and Haines Young
In addition to the waterfall model described above, the lower left corner of the figure describes the economic value of ecological diversity directly through the trading behavior of the market, that is, the economic cost that people are willing to pay for an extra unit of ecosystem diversity. To assess the economic value of ecological diversity.
Uncertainty ecology, the economic value of diversity
In the yellow box in the upper left corner of Figure 1, another method for assessing the economic value of ecosystems is also listed, which deserves special attention. The value in an uncertain environment. For example, in the future, as the economic system changes, (a certain plant has medicinal value) , or due to technological advances (black technology inspired by the biomimicry of a certain creature) , people ’s valuation has significantly improved, so that society as a whole , Willing to pay more value in order to protect ecological diversity.
Another situation is that when ecosystems face external disturbances, ecological diversity provides insurance-like functions. Economic loss.
The value that ecological diversity provides in an uncertain environment is itself faced with a lot of cognitive uncertainty. An assessment method is similar to hedging in financial markets. By selecting a group of financial assets whose changes have nothing to do with external shocks or which show negative correlations under external shocks, the relative stability of the yield can be guaranteed. Similarly, if the species that make up ecological diversity face some kind of external shock, some will flourish and some will decline. This kind of asynchrony makes the overall ecosystem stable. The extent to which ecosystem fluctuations are reduced,As an “insurance” value brought by ecological diversity in an uncertain environment.
Learning from the terminology in finance, this mechanism is called the “insurance effect” of biodiversity ( (portfolio effect; Tilman 1999) .
Four relationships between biodiversity and its economic value
Concave and convex functions are two concepts in mathematics that describe whether the acceleration of change is positive or negative. If it is a concave function, then the change will be faster and faster, and if it is a convex function, the initial change will be fast, but later it will not be so obvious. The following figure exhaustively enumerates all possible relationships between ecological diversity and its economic value in the academic world, which are monotonically increasing concave functions (A) Monotonically decreasing convex function (B) , complete concave function (C) , the complete convex function (D) , where the horizontal axis in the figure represents ecological diversity, and the vertical axis represents the corresponding diversity. Economic value.
Figure 2: Biodiversity and its economic valueSchematic diagram of four kinds of relations-monotonically increasing concave function
The consensus of traditional ecology is that the economic value of biodiversity is shown in Figure 2. When the diversity is reduced from 15 to 10, compared with when it is reduced from 10 to 5, its value decreases even less, that is, protection The value of ecological diversity will become increasingly apparent as the diversity of the ecosystem itself decreases.
Figure 3: Schematic diagram of four relationships between biodiversity and its economic value-monotonically decreasing convex function
However, this review, through a literature review, finds that this is not the case. This means that If the economic value of ecological diversity is as shown in Figure 3, the protection of the original ecological environment appears to bring greater economic value than protecting the already developed ecosystem.
Figure 4: Four schematic diagrams of the relationship between biodiversity and its economic value-complete concave function
If the description in Figure 4 is consistent with the facts, then the more ecological diversity is not the better, but there is an optimal value.
Figure 5: Four schematic diagrams of the relationship between biodiversity and its economic value-complete convex function
If the description in Figure 5 is true, it means maintaining the damaged ecological diversity, instead of further reducing the ecological diversity of this area and obtaining higher economic value. Therefore, understanding the relationship between ecological diversity and its economic value has significant practical significance.
Empirical research on diversity and economic value
Look at a few specific examples. In agricultural production, if one piece of land is planted with only one crop, the yield will be better, and if more than one is planted, it will lead to a reduction in average yield. However, in the case of pests or droughts, after planting multiple crops, fluctuations in yields will be reduced. This can be seen as the “insurance” value provided by ecological diversity. The following figure shows the value of the output value of farmland after adding more crops to the farmland that only grows bananas. (the horizontal axis is the number of crops planted) Change curve, where the value is the sum of the two parts of risk insurance under the condition of return and uncertainty. It can be seen from the figure that in the farmland environment, the economic value of ecological diversity is not a traditionally considered monotonically increasing concave function, but a convex function, that is, there is an optimal number of crops that can stabilize the farmland High yield.
Figure 6: The relationship between the number of crops in the farmland and the economic value of the farmland comes from supplementary materials
Figure 7: The relationship between grassland ecological diversity and its economic value
Then examine the relationship between the ecological diversity of grassland and its economic value. In addition to grassland can provide animal husbandry, and then provide economic value. (blue) In addition, the grassland ’s carbon sequestration capacity (absorbing carbon dioxide) should also be considered as the economic value service provided by grassland (purple) , plus the economic value of commercial forest land on grass (green) , you can Calculated as the total economic value of the grassland. It can be seen from the figure that whether it is carbon sequestration or commercial value, the changes in its diversity (horizontal axis) are convex functions.
Summary and Research Prospects
People who are interested in the personality of nature, focus on the diversity of species and communities; people who are interested in the overall ecosystem, focus on the functions of system organization; people who are interested in socioeconomic and human interests, Focus on the well-being and value that the environment and resources can bring to human society. Ecology (Ecology) , Economics (Economics) , The roots are all Latin Eco, meaning “home”, the cognition of ecosystem and economic system is originally the same.
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