Analysis of Eco-economic Effects of Karst Rocky Desertification

Karst rocky desertification is not a simple bare bedrock phenomenon. In the fragile karst environment, once it happens, it has a strong eco-economic effect, affecting resources, environment and regional poverty in karst areas (photo 5- 1).

I. Resource effects

Rocky desertification is the result of reverse mutation and succession of karst natural ecosystem under the impact of population explosion. With the expansion and deepening of the degree and intensity of rocky desertification, the supply capacity of natural resources is under great pressure, the hematopoietic function of nature's own resources is destroyed, and the stock of resources drops sharply.

The main feature of rocky desertification is the "desertification" landscape on the surface, and the green plants on the surface gradually give way to the bare bedrock after being destroyed. The abdication of plants not only means the reduction of forest resources, but also means the reduction of habitats of many animals and the source bank of plants. The promotion of rocky desertification reduces the variety and quantity of the whole biological resources, and the biological field is sparse and withered.

Due to the dual three-dimensional geographical structure of surface and underground systems, water resources in karst basins are often weak, such as "surface water is as expensive as oil and groundwater is rolling", and the surface system has poor water storage and water retention capacity. The water storage and conservation function of ecosystem is determined by the interaction between surface vegetation and soil. Experiments show that in forest areas, there is no surface runoff and the daily rainfall is 30 mm; The daily rainfall is 55 ~ 100 mm, and it takes 3 days to see the fine water flowing out. When the rainfall in that year was 1200mm, the water loss in the forest area was only 50mm, while under the same environmental conditions, it could reach 600mm. An acre of forest land stores at least 20m3 more water than the forest area.

Good vegetation can also increase the horizontal rainfall, and the rainfall in forest areas is 50 ~ 250 mm more than that in non-forest areas 50 kilometers away. This phenomenon decreases with the shrinking of forest area and disappears with the disappearance of forest (Mao Wenyong, 1998). In karst areas, the ability of vegetation to conserve water resources is particularly important for the utilization of water resources, especially agricultural water use. The emergence of rocky desertification makes the karst vegetation with strict requirements for habitat decline in reverse succession, and the cultivated land without vegetation protection is seriously short of water. After vegetation destruction, the water conservation ability is reduced and the river flow is generally reduced.

Rocky desertification is not a natural bare rock, and its development process is accompanied by soil erosion and the decline and loss of land productivity. In Guizhou karst land, except for most of the land with good precipitation conditions (including the bottom of wide and shallow depressions), due to the poor original land conditions, low utilization habits and development level, extensive land use, slash-and-burn phenomenon is common, land reuse and light tillage, extensive planting and thin harvest are the most basic conditions, land fertility is gradually lost, and land degradation and rocky desertification appear. In the rural areas where rocky desertification occurs, because the rocky desertification land is extremely barren, farmers often increase food production by simply reclaiming more wasteland. However, under the backward production mode of extensive farming and extensive management, the increase of per capita cultivated land area can not correspondingly increase per capita grain. On the contrary, because there is no uncultivated low-slope cultivated land in Guizhou Province, there is almost no reserve land resources. Expanding cultivated land area can only mean the deepening of steep slope reclamation, which will lead to serious soil erosion and the spread of rocky desertification land. Strong soil erosion causes sloping farmland to be washed away and flooded, farmland to be washed away, ponds and reservoirs to be silted up, and soil nutrients to be greatly lost. In turn, it leads to the decline of land productivity, the deterioration of ecological environment and the low and unstable crop yield.

After the surface soil in karst area is eroded, the nutrient content and land productivity of the remaining lower soil are obviously reduced. Xuhui Chen (1997) According to the determination, the content of organic matter in the topsoil of yellow soil dryland is 1.4 1%, and the available potassium is 1 10.4mg/kg. However, after erosion, the organic matter content in the subsoil of yellow soil is 0.85%, and the available potassium is 75.6mg/kg. Under the condition of no fertilization, the yield of soybean planted in the lower soil is only 15.6% of that in the top soil. The yield of broad bean in subsoil is only 1 1.4% of that in topsoil. Deng Peiyan (1999) studied for a master's degree thesis. Based on the basic principles and methods of environmental economics, in view of the severe situation of soil erosion in Guizhou, the physical losses caused by soil erosion, such as N, P, K, soil conservation and rainy season, were selected as indicators of economic losses of soil erosion, and the monetization results of economic losses of soil erosion in Guizhou were estimated from both on-site and off-site, and the monetary value of economic losses of soil erosion was compared with the main indicators of economic construction. The results show that the economic loss of soil erosion in the whole province from 65438 to 0999 is 2202 158700 yuan, accounting for 2.22% of GDP.

Therefore, karst rocky desertification has caused a vicious circle of "wasteland-land reclamation-land degradation-land reclamation", and the deterioration of rocky desertification land resources has reacted on natural resources and started the mechanism of vicious circle. At present, rocky desertification in Guizhou karst area has rapidly developed into a prominent aspect of Guizhou's environmental problems. The rocky desertification land is increasing, and the area of light rocky desertification has reached 35,900 km2, which makes the already scarce land resources worse.

Second, environmental impact.

The background of rocky desertification is the fragile ecological environment of karst. There is no transition structure between the surface of carbonate rock and the overlying soil layer, and the contact surface is a well-defined superposition relationship, so the interdependence between them is poor. At the same time, the surface of carbonate rock under the soil layer is a chemical erosion surface, and chemical erosion will occur when precipitation permeates the rock surface. Because the physical erosion rate in karst area is much higher than the formation rate of weathering residue, the regional soil particles show negative growth, and the bound soil layer will be eroded and rocky desertification will occur. Therefore, karst environment provides a unique geological background for rocky desertification.

Karst ecosystem has its unique particularity. In the process of positive evolution, it will gradually form a benign ecological environment like Maolan forest in Guizhou, but it has the fragility that the soil is more difficult to maintain. Due to the rapid population growth, which exceeds the suitable land carrying capacity, the imbalance of resources, environment, population and economy in Guizhou has brought heavy pressure on the ecological environment in this area.

Once there is a slight rocky desertification, the karst environment will enter the reverse evolution process. Facts have proved that it takes hundreds of years for karst areas to evolve forward, such as the formation of Maolan forest in Guizhou, and it only takes decades or even years for karst areas to reverse from forest to the top state of strong rocky desertification. Because the physical erosion rate in karst area is much higher than the formation rate of weathering residue, the regional soil particles show negative growth, and it is extremely difficult to change from intensity rocky desertification to benign cycle. The positive succession of karst environment is slow and the reverse succession is fast.

Rocky desertification will have a negative effect on the ecological environment, and the ecological environment will further weaken vegetation due to the loss of growing soil. Under the humid climate conditions and steep and undulating surface conditions in Guizhou, the soil without vegetation protection is more likely to be lost. Soil erosion in Guizhou loses 204.4 ~ 3.65 t of soil, 296 million ~ 529 million kg of total nitrogen, 840 billion ~ 654.38+500 million kg of total phosphorus and 654.38+586 million ~ 2.832 billion kg of total potassium every year. Only one nutrient element is lost in the soil, with an annual loss of 5.2 billion-9.296 billion RMB. At present, the area of soil erosion in karst distribution area has reached 42,400 km2, and the average intensity of soil erosion is 3 1.69t/a? Square kilometers. The vicious circle of soil erosion and rocky desertification has deepened the further deterioration of karst ecological environment.

At the same time, with the sharp decline of forest resources and the deterioration of ecological environment, natural disasters such as drought, flood, hail and debris flow occur frequently in Guizhou, among which drought and flood are the most serious. The province has a mild drought in three years, a moderate drought in five years and a severe drought in ten years. Drought usually lasts for 30 days in a year, and severe drought lasts for more than 60 days, up to 80 ~ 90 days at the longest. The flood disaster area in Guizhou accounts for 55% of the total area of the province. Every year, all counties (cities) in the province have different degrees of flood disasters on average, among which Qianxi, Northwest Guizhou and Southwest Guizhou suffer the most frequent and serious disasters. In early July, a once-in-a-century rainstorm occurred, 1996, and 59 counties (cities, districts) in the province were affected, with 2 14 people dead and seriously injured 1380 people.1000 people were trapped by water. 1985 a rainstorm in Qinglong county caused 6 landslides, 9,496 households were seriously injured, 44 people died, and 2 reservoirs and/kloc-0 power station were washed away. In July of the same year 1, a landslide occurred in Zhujiazhai Village, Longtan Township, Shuicheng County, which washed away more than 50 houses and killed 30 people. Due to frequent droughts and floods, serious soil erosion has been caused, and the quantity and quality of cultivated land have declined. It can be seen that the lesson at the expense of the environment is profound. History has fully proved that violating the laws of nature is bound to be punished by nature. At the same time, the harsh reality has awakened us, and it is time to protect forest vegetation, control rocky desertification and build ecological environment.

Karst ecosystem is porous, prone to drought and soluble at room temperature, and its vulnerability and capacity characteristics are similar to those of desert edge (Yuan Daoxian, 1989). Even in the karst environment with good quality, pollution-free, benign ecosystem evolution and slight human disturbance, their population structure and biomass are simple and low, reflecting the harsh and fragile environment (Yang Hankui,1989; Yang Mingde, 1990). For example, the green biomass (149. 123t/hm2) of karst forest community in Maolan is much lower than that of non-karst forest in the same niche, which is only equivalent to the edge of desert (150t/hm2) and has low environmental capacity (Yang Hankui, 1994). The occurrence of rocky desertification leads to the fragility of karst environment, which is difficult to recover once it is destroyed, and accelerates the degradation of the destroyed ecological environment. The climax of its evolution will lead to the collapse of the ecosystem. The negative impact of rocky desertification on the environment is extremely serious.

Third, the poverty effect.

Guizhou mountainous area has a special geographical environment of "eight mountains, one water and one field", and poverty and backwardness are still the biggest limiting factors for economic development in mountainous areas. By 1999, there are still 2.74 million rural poor people in our province, and the per capita income is below that of 400 yuan (1997 standard), so it is very difficult to solve the problem of food and clothing. Poverty in karst areas with poor living conditions in Guizhou has its special natural, social and economic reasons. In the process of historical succession, many factors have formed and aggravated absolute poverty and relative poverty. Many mountainous areas are areas where economic poverty is concentrated in our province, and most of them belong to remote karst mountainous areas where ethnic minorities live together. These backward mountainous areas have low self-regulation ability and high ecological sensitivity and vulnerability.

Poverty-stricken areas are not only economic poverty, but actually the root of poverty is often the low quality of the population, especially the low quality of the minority population caused by historical reasons. In the vast poverty-stricken areas, the primary manifestation of poverty is far from adequate food and clothing, with meagre income and only subsistence production. In order to survive, it is bound to show a series of characteristics in behavior, such as ultra-low income, increasing population, weak thinking ability, not knowing why or unable to change the fate of poverty, poor thinking, but often helpless; Indiscriminate cultivation and cutting, extensive planting and thin harvest, "burning a mountain, planting a slope, harvesting a basket and cooking a pot" are the main characteristics of agricultural production in poor areas, which are in sharp contrast to intensive cultivation in Bazi area. This is of course necessary for farmers, but it aggravates the deterioration of the ecological environment and leads to further poverty in fact, thus making the rocky desertification in Guizhou enter a vicious circle. In order to solve the problem of food and clothing for the growing population, people's solution is often simply to care only about the immediate interests of land reclamation. The result of backward production in extensive management is revenge from nature. The emergence of rocky desertification and the continuous expansion of the area have led to the decrease of cultivated land resources year by year, the land is becoming more and more barren, the fertility is declining, the water conservation capacity is poor, and the grain output is low and unstable, which seriously restricts the economic development in mountainous areas and keeps the farmers in poverty for a long time. The continuous deterioration of the ecological environment in rocky desertification areas has made human beings in some places completely lose the basic conditions for survival and forced to move to other places. In a sense, rocky desertification and poverty are inseparable twin brothers. The direct victims of rocky desertification and poverty are human beings, who are the founders of this "He is my brother". After the excessive population growth, excessive logging is closely combined with reclamation and low population quality, and * * * isomorphism has become the overall social and economic characteristics of poor areas, with single production structure, backward social culture, strong isolation and lack of talents, which in turn has continuously aggravated the further poverty in poor areas and aggravated the increasingly serious rocky desertification.

Rocky desertification accelerates the decline of land productivity, reduces the environmental carrying capacity, reduces the utilization rate of water resources, makes drinking water difficult for people and livestock in rural areas, and gradually makes local people lose their living conditions. One side can't support the other side, and serious areas have become a typical example of poverty alleviation through population and environmental migration. For example, in Mashan and Yaoshan areas, karst and rocky desertification are obvious, the mountains are all stones, the ditches are all dry river ditches, and the slopes are all steep slopes. There are stones everywhere, and after the land is broken into hundreds of stones, it can only be pieced together into an acre of land. People describe it as "straw hat land" and "dustpan land", which is the land on which they live. More than 80% of farmers live in thatched huts and forked houses, lacking salt and food, and even kerosene lamps can't be lit all year round. This is a very common phenomenon in the "two mountains" area. There is also a terrible poverty. Children who can't afford to read can be seen everywhere in the "two mountains" area. Many children aged 65,438+00 have never seen what money looks like. At the age when I was supposed to be studying, I dropped out of school because I couldn't afford a few dollars in tuition. The hand that should have held the pen took the long cow rope. In addition, Huajiang Grand Canyon with serious rocky desertification is a famous poverty-stricken area with obvious height difference, steep slope, thin soil, bare rocks, dryness and water shortage. The root of poverty is the special geographical environment and the disharmony between man and land.

Of the 86 county-level units in Guizhou, 75 counties (cities) belong to "karst counties", and the population density of these karst areas is 223. 1 person /km2, of which the population density of rocky desertification areas with 4 1 county (city) is 225.2 person /km2. According to the characteristics of karst mountain areas in Guizhou, the population density is 100 people /km2, and unreasonable reclamation and soil erosion will occur if the population density exceeds it. When it reaches 150 people /km2, rocky desertification will occur and the environment will enter a vicious circle (Yang Hankui, 1992). The huge population pressure in Guizhou forces people to carry out intensive predatory production of land, and the contradiction between man and land is sharp. In Guizhou karst land, most of the land with good precipitation conditions except dams (including the bottom of wide and shallow depressions) is widely used because of poor original land conditions, low utilization habits and low development level, and slash-and-burn farming is widespread. It is the most basic situation that the land is reused and cultivated lightly, and the extensive planting is low. The appearance of rocky desertification accelerated the land degradation and gradually lost the land fertility.

In the rural areas where rocky desertification occurs, because the rocky desertification land is extremely barren, farmers often increase food production by simply reclaiming more wasteland. However, under the backward production mode of extensive farming and extensive management, the increase of per capita cultivated land area can not correspondingly increase per capita grain. On the contrary, because there is no uncultivated low-slope cultivated land in Guizhou Province, there are few reserve land resources. Expanding cultivated land area can only mean the deepening of steep slope reclamation, which will lead to serious soil erosion and the spread of rocky desertification land. Strong soil erosion causes sloping farmland to be washed away and flooded, farmland to be washed away, ponds and reservoirs to be silted up, and soil nutrients to be greatly lost. In turn, it leads to the decline of land productivity, the deterioration of ecological environment and the low and unstable crop yield. The results show that the nutrient content and land productivity of the remaining lower soil are obviously reduced after the surface soil erosion.

According to the investigation of 9 villages such as Luojiaqiao and Gaoshanbao in the upper reaches of Hongfeng Lake in qingzhen city, rocky desertification mountainous areas have occupied 16.39% of the land area, and the forest coverage rate only accounts for 5.5%, so the ecological situation is very severe. Deforestation, releasing Yamakaji, land reclamation on steep slopes and predatory management have not stopped in some places, causing serious soil erosion and accelerating rocky desertification and semi-rocky desertification. Some places have lost the basic living conditions of human beings. Severe ecological situation and the root of poverty.

Of the 48 national poverty-stricken counties in Guizhou, 39 are located in rocky desertification areas, and there are still millions of poor people. Eliminating poverty is the basic premise of realizing the sustainable development of regional eco-economy in China, and it is also the historical responsibility of local governments. Ecological environment construction in Guizhou is an important part of the national strategy of developing the western region, and the ecological environment problem is mainly "rocky desertification". Rocky desertification control is the primary task of ecological reconstruction in karst areas. Chapter 8 "Poverty Eradication" of China 2 1 Century Agenda lists poverty alleviation in southwest karst areas as a key poverty eradication project in the near future, and poverty alleviation in Guizhou is mainly in rocky desertification areas. The relationship between rocky desertification and poverty is always reversible, whether in karst areas, plateau areas and canyon areas divided by county level. Although man is the founder, he is also the reaper. Only by dealing with the relationship between rocky desertification and poverty at the same time can we bid farewell to poverty and usher in a better tomorrow.