As a biodiversity researcher, why do I go where I often go with landslides? It turns out that this is not a coincidence

I am a biodiversity conservation researcher whose focus is on montane forest ecosystems.

I am often asked: What are the dangerous moments when I go out into the wilderness?

When I think about it, there is no danger in being prepared – but there are some things that cannot be predicted and prepared for, and that is "natural disasters.".

Why do I experience landslides so often?

When I go out into the wilderness, my biggest fear is landslides and flash floods, especially during the annual rainy season.

Every year, our team spends a few months in the Southwest Mountains, which are important biodiversity hotspots on the mainland. We try to get the job done before the rainy season, but in recent years we have found that the rainy season in the Southwest is coming sooner and later, ending later and more intensely.

During the rainy season, you can never predict the time you need to spend on the road, encounter landslides large and small, block the road or go to the area where you can't work because the road is broken, or go to the work area but there is no way to go up the mountain, which is the norm of the rainy season.

One year, we were driving from Sichuan to Qinghai, and there was a long stretch of road, with a towering mountain wall on our right hand and a deep valley in our left hand, and the car was on a winding mountain road. When I turned a corner, the car suddenly stopped. At first glance, there was a car parked not far in front of us, constantly flashing double-flashing. It turned out that just a few minutes earlier, a landslide had poured down from in front of it. The road is broken. Later, I learned that we were lucky because a few days ago, a car was buried directly by a landslide.

Wen County in Gansu, Qionglai Liangshan in Sichuan, Shuangbanna in Ailao, Shanxi in Yunnan, Liupanshui in Bijie, Guizhou... After walking through different areas, I found that the landslide marks were like scars carved there, which were difficult to ignore.

The landslide traces are like a scar 丨 the author took pictures

And this kind of trauma is still happening repeatedly.

Every time I see in the news the areas I have investigated destroyed by landslides and mudslides, the roads and villages that have been rebuilt over and over again after the disaster, or the construction workers who have been taken to their lives during the rush repairs, I am extremely worried. Worried about property damage, more worried about people's safety.

Gradually, I will also have doubts: the mountains are difficult to climb, the rain is heavy, and the slopes will be landslides at every turn... Why do the areas we work in always feel more difficult than other areas? In other words, in areas where we often do biodiversity research, why do landslides seem to occur more frequently? Is there any inexplicable connection that explains all this?

This question also prompted me to start a research project to see the relationship between biodiversity and landslides in China and the world.

Together with my collaborators, I collected information on the distribution of all known birds, mammals, and amphibians around the world. We pay particular attention to species with small distribution areas, as areas where these species are concentrated often represent hotspots where endemic species are concentrated. When these areas are damaged, it is difficult to find these species in other parts of the world, which means a higher risk of extinction.

A-C represents the area where species are concentrated in the narrow area of birds, mammals and amphibians, and D represents the landslide susceptibility distribution (Li et al., PNAS, 2022)

At the same time, we used spatial data on global landslide susceptibility based on the factors that led to landslide susceptibility to look for a correlation between landslide susceptibility and biodiversity.

Areas with a high degree of agreement between biodiversity and landslide susceptibility were shown as purple with a significant positive correlation (Li et al., PNAS, 2022)

The results answered my previous doubts. It turns out that this is not a matter of my personal choice of area of work, but a universal phenomenon: areas with a high global landslide risk also happen to be the areas with the highest biodiversity; those where narrow areas and endemic species are concentrated tend to overlap highly with areas at high risk of landslides — they are concentrated in specific mountainous regions around the world, of which Asia is one of the most concentrated areas.

Why is there such a strong link between biodiversity and landslide risk?

This is because landslide-prone areas tend to be close to active geological activity zones with high topographic undulations. At the same time, such elevation differences, geographical isolation and active orogeny also provide the basis and evolutionary impetus for the formation of species here – which may also explain why mountains have the richest biodiversity: mountains, which account for only about 25% of the world's land area, have more than 85% of species, including birds, mammals and amphibians.

The Faye's langur, defined by the IUCN as an endangered primate, is only found in southern Yunnan on the mainland

Common threats:

Land-use change and climate change

In our research, we also found that biodiversity loss and landslide risks not only overlap spatially, but also face very consistent threats: land-use change and climate change.

Land-use change causes habitat loss and fragmentation of many species, which is one of the most important causes of biodiversity loss. Under human activities and transformation, more than 3/4 of the ice-free land has not been restored, more than 85% of the wetlands have been lost, and forests are disappearing at a rate of 10 million hectares per year... These cause wildlife habitats to disappear at an alarming rate, eventually leading to a decline or extinction of species populations.

In order to reclaim farmland, forests are often set on fire in Myanmar 丨 Author's photograph

Climate change can mismatch species' life history with changing environmental conditions, leading to decreased reproduction and viability, while habitat loss and fragmentation deprive species of the material conditions to adapt to change – no corridors, no habitat, and no migration to more suitable areas. According to a study released in 2020, if climate change trends are not curbed, at least 1/3 of species will become extinct by 2070.

These two important threats to biodiversity extinction happen to be the two most important factors that increase the risk of landslides and trigger it – but the reason behind this is not just a coincidence.

So, how do land-use change and climate change affect landslides?

Let's start with land-use change. Activities such as large-scale infrastructure construction, road construction and deforestation can undermine surface vegetation and slope stability, thereby increasing the risk of landslides.

To some extent, the natural vegetation on the mountain is equivalent to a stable protective layer of the slope. The root system of the plant is like a large net in the ground, intertwined, you can grasp the soil in it; the root system extends downwards, and some can be rooted into the rock layer below, like anchors to fix the soil layer as a whole, especially when the root system is relatively deep, it can make the entire soil - root protective layer thicker, and the substrate is tightly integrated, reducing the occurrence of shallow landslides.

However, human activities lead to changes in land use, stripping this protective layer like a razor. Under the same rainfall conditions, areas that have lost their natural vegetation type are more likely to experience landslides. Between 2004 and 2016, deadly landslides caused by deforestation, the construction of large and small infrastructure and mineral extraction accounted for 16% of all incidents.

In Yunnan, the landslide caused by road construction丨 Author photographed

Abnormal precipitation is the most important straw that triggers landslide events. Heavy rainstorms or low-intensity prolonged rainfall can induce landslides. Rainwater infiltration increases the weight of the soil layer, while accumulating water on the inlet in the lower part of the slope reduces the shear strength and leads to landslides.

With climate change, extreme precipitation events will become more frequent and intense in the future, potentially inducing more landslide events.

For example, at the beginning of this year, South America was generally affected by heavy rainfall, which triggered many landslide accidents. On January 13, torrential rains in many parts of Bolivia triggered large-scale landslides that affected more than 60,000 families; on January 31, the Ecuadorian capital died and injured at least 28 people and injured 52 people due to heavy rainfall; on February 8, heavy rainfall in Colombia's Pereira region triggered landslides, killing at least 14 people and injuring 35 people...

The study found that in the alpine regions where the Himalayas and the Tibetan Plateau transition in Asia alone, the frequency of landslide events will increase by 30-70% by 2100 due to the increase in extreme precipitation events. With climate change, more frequent and extreme precipitation will increase the risk of landslides in mountainous areas, threatening local residents and economic productive activities.

Mudslides and landslides caused by exceptionally heavy rainstorms in Pingwu, Sichuan Province, have severely affected the surrounding communities丨 Courtesy of the author

landslide risk high risk areas,

Development is needed differently from plains

While doing this research, I've been asking myself —

We want to protect biodiversity, we want mountains not to be destroyed by human activities, does that mean "asking people here not to develop"? Because of the inconvenience of transportation, the mountainous areas with high risk of natural disasters are often economically backward areas, if they have not been developed, is it fair to the local area?

The link between landslide risk and biodiversity, and the fact that both face the same threat factors, is a reminder that it is not that there should be no development here, but that there is a need for a development approach that is different from that of the plains, and that a suitable development model needs to be found here according to the sensitivity and vulnerability of the mountains. In mountainous areas, natural ecosystems are not an obstacle but a barrier against risk. Sustainability and resilience are the key words to consider for development here.

For researchers, it is not enough to provide relevance, we also need to give more accurate information to help actual decision-making and planning. So, in this study, we also identified specific areas that need to protect and change development patterns based on different criteria.

First, we identified the current high-risk mountain areas, that is, mountainous areas with high biodiversity and high landslide vulnerability. There are 247 mountain systems in the world, china is the largest, with 36 mountainous areas listed. These areas are mainly distributed in the Hengduan Mountains, the Himalayas, the Yunnan-Guizhou Plateau, the Qinling-Daba Mountains, the Nanling Region, and the Wuyi Mountains.

In addition, we identified high-risk mountainous areas that will emerge in the future. For areas with high biodiversity but little risk of landslides now, we identified some areas that "may not be high-risk mountain areas now, but will enter the list of high risk of landslides in the future" based on climate change models and land-use change prediction models, and we define them as "future focus areas", such mountains, a total of 31 in the world, mainly concentrated in South America.

High-risk mountainous areas, which are and will emerge now or in the future, should be avoided by traditional development models. The development of these mountainous areas requires more scientific planning, whether it is the construction or reconstruction of large infrastructure, a more comprehensive risk assessment is required.

At present, climate change cannot be reversed quickly, and what we can do is to enhance the protection of existing ecosystems and restore damaged natural systems. Green water and green mountains are actually a natural insurance.

Previously, when we visited some of the often affected areas of Sichuan, we often observed that those places that had been cut down were more likely to have mudslides and landslides when heavy rains came, while those that had not been cut down and still had primary forests rarely appeared – this is actually a warning: the destruction of natural vegetation in the past may lead to repeated natural disasters. Then, when planning the development of mountainous areas, it is necessary to think that those long-term security barriers cannot be destroyed for short-term prosperity.

In addition, the location of the new area also needs to be considered, and it is best to avoid high-risk areas. In order to facilitate transportation, many areas will relocate alpine residents to low roads. However, road construction will make the surrounding area more susceptible to landslide risk. Many of the new areas are often where river valleys are located, and when the rainy season comes, either the foundations of the roadbeds are washed away by floods or destroyed by landslides and mudslides.

In addition to "new construction", there is actually an important problem: reconstruction.

Whether those existing facilities should be repeatedly rebuilt is also a question.

Every year during the rainy season, some mountainous areas in the southwest suffer from mudslides and landslides caused by heavy rains, and houses are damaged in large areas or even completely buried. After the rainy season, a lot of money was invested in post-disaster reconstruction, cleaning roads and rebuilding houses – but when the rainy season came the following year, landslides and mudslides occurred in the same place. If we rebuild and invest in the disaster over and over again, but we can't resist these disasters, perhaps we should think about whether it is worth repeatedly playing with disasters at the risk of economic and life loss, and whether it is time to give up on using and living here. Perhaps the choice to avoid or evacuate high-risk areas is, in some cases, a wiser choice.

"Forest vegetation restoration" is not only more scientific,

The economic account is also cost-effective

Some people may say that our technology is so developed, there must be some facilities that can help resist the impact of landslides, such as building some retaining walls, protective nets and other structures.

But in fact, these structures can protect some rockfall and small landslides, and buy evacuation time for the surrounding population, but it is difficult to rely on them to reduce the impact of landslides and reduce the impact of large landslides - these facilities will either be flooded by landslides or will slide down the mountain with the slides.

Instead of repeatedly investing in reconstruction and reconstruction, it is better to establish protected areas to maintain the strong root network of native vegetation and the natural adjustment and balance mechanism, or to restore vegetation in areas destroyed by humans, giving nature time to repair its barrier role against impact and risk.

Healthy forests are rich in plant species and vertical structure 丨 Author photographed

Previously, we tried to persuade people and policymakers to support habitat conservation and restoration through the perspective of biodiversity conservation, but often it was not effective. Now, we have a strong proof: habitat conservation and restoration is not only for wildlife, but also for the safe development of human beings themselves.

Disaster mitigation through nature conservation and restoration not only has scientific support, but also is more cost-effective in terms of long-term economic account. For example, a study in the Colombian Andes found that the cost of reducing the impact of landslides through forest vegetation restoration is only 1/17 of the cumulative cost of traditional and repeated post-disaster reconstruction and repair of damaged facilities. This is a nature-based solution that achieves disaster reduction through forest protection and restoration. In the context of climate change, this would be the most productive and costly way to do this.

So, how to restore "forest vegetation restoration"? Is it to plant a lot of trees?

Not.

Because the forest is not a simple superposition of trees, there are many problems that need to be considered comprehensively. True vegetation restoration should be determined for local native vegetation: if it is a meadow, the grass should be restored, and if it was a shrub before, the shrub should be restored. Not all places should plant trees, and especially for landslide surfaces, the pioneer community dominated by herbaceous shrubs that are naturally restored under unstable structures is easier to achieve the effect of solid slope; on the contrary, if some fast-growing tree species are blindly selected, it seems to quickly recover green, but these tree species often have roots that are not deep enough, but they are more likely to landslide.

A single species planted is vulnerable to landslides丨 Author photographed

Let me give you an example. Not long ago, I saw a news article that mentioned that the Winter Olympics have brought about a ski boom and the rapid development of domestic ice and snow venues, and by the beginning of 2021, there are 654 standard ski resorts in the mainland, an increase of 317% over 2015.

It is conceivable that as the number and demand for skiers increases, the pace of construction of ski resorts in the mountains may accelerate in the future. Before construction, it needs to be carefully assessed: is it suitable for a snow field?

Now, in addition to the economic ledger, this assessment has another consideration: environmental risks. Ask experts or look for information during the pre-construction assessment to find out: Is there a lot of biodiversity here? Because this richness may be highly correlated with environmental risks, which in turn means that there is a relatively high risk of landslides, and if the forest is shaved here, the ski resort is developed, and the foot of the mountain is dug up to build roads and houses, it may make the place that is prone to landslides lose protection and stability.

In a way, "biodiversity" is like the patron saint who protects our long-term tranquility. But like Pandora's box, the more beautiful and seductive the appearance, the more disasters and diseases may be guarded. If we open the box arbitrarily and destroy the original shackles, we may only put hope at the bottom of the box in panic, but we will never be able to restore the peace and beauty of the past.

Don't open the box arbitrarily – for the sake of all living beings and ourselves, to survive more securely.

bibliography

[1] Li B.V.*, Jenkins C., Xu W. (2022). Strategic protection of landslide vulnerable mountains for biodiversity conservation under land-cover and climate change impacts. PNAS,119(2) e2113416118.

[2] D.Sanderson, A. Sharma, World Disasters Report 2016. Resilience: Saving Lives Today,Investing for Tomorrow (International Federation of Red Cross and RedCrescent Societies, 2016).

[3] A. Schild, ICIMOD’s position on climate change and mountain systems. Mt. Res. Dev.28, 328–331 (2008).

[4]https://globalnews.ca/news/6494727/sasquatch-mountain-landslide-trapped/

[5]https://pubs.er.usgs.gov/publication/ofr96701

[6]https://www.who.com.au/thredbo-landslide-what-happened-at-the-thredbo-disaster

[7]https://nhess.copernicus.org/articles/21/147/2021/

[8]https://edmonton.ctvnews.ca/landslide-closes-part-of-grande-prairie-adventure-park-indefinitely-1.4947198

[9]https://unofficialnetworks.com/2020/10/06/italian-ski-resort-landslide/

[10]https://www.sport.gov.cn/n20001280/n20745751/c23955009/content.html

Author: Li Binbin

Editor: Malt Yang

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