Nature: biodiversity loss caused by land use change can be reversed

According to an article entitled "Global Land use impacts on Local Terrestrial Biodiversity" (Global effects of land use on local terrestrial biodiversity) published online by Nature magazine on April 1, 2015, land use change caused by human factors has reduced the average species richness, total richness and sparse richness in local areas by 13.6%, 10.7% and 8.1% respectively since 1500. In the long run, 3.4 per cent of global biodiversity loss is expected by 2100, but this trend can be reversed by strong mitigation measures.

Human activities, especially habitat change and degradation, lead to the decline of global biodiversity, which in turn affects ecosystem functions and services. The researchers used datasets of biodiversity trends and the most representative models of geography and taxonomy to quantify the response of terrestrial biodiversity to land use and related changes. The results show that richness, sparse richness (species richness analyzed by sparse method) and total abundance are most affected by land use and land use intensity, but are less affected by other variables. however, there is a close relationship between these less influential factors. The species richness and total richness decreased slightly in the areas with the highest population density, and decreased in areas close to roads and transportation. The richness, sparse richness and total abundance in the areas with the most serious habitat damage were 76.5%, 40.3% and 39.5% lower than those in the less damaged areas, respectively.

The results show that under the same land use model, the community composition is similar, in which the primary vegetation and secondary vegetation communities are the most similar, while the communities of artificial forest, grassland and cultivated land form different biological communities. Under the human-dominated land use model, the average plant height of plants is lower than that of primary and secondary vegetation, and decreases with the increase of population density. The average mass of animals does not always change with land use or population density, but with the distance from the nearest road.

The researchers made a global map of local biodiversity distribution with a resolution of 0.5 °× 0.5 °. It can be seen that the biodiversity in human-dominated areas is much more lost than that in areas still growing with natural vegetation. The average richness of the most affected grid cells is reduced by 31%, which can significantly change the function of the local ecosystem. 1.7% of the grid cell species richness increased, with an average increase of 4.8%. The changing trends of total abundance and sparse richness are about the same. The results of global spatial model inference show that species richness declined most rapidly in the 19th and 20th centuries compared with those without human influence. By 2005, the pressure of land use and related factors reduced local species richness by an average of 13.6%, total abundance by 10.7%, and sparse richness by 8.1%.

The simulation results of global biodiversity changes under four different concentration pathways (RCP) scenarios show that the net changes of biodiversity vary greatly between regions and countries in 2095. In the context of minimal climate change (IMAGE2.6, where native vegetation is rapidly converted into crops and biofuels), biodiversity loss ranks second, which does not mean that low-emission scenarios have to bear the consequences of significant biodiversity loss; in Mini CAM4.5 (mitigation of climate change through carbon markets, crop improvement and dietary change), the average global richness will increase. Under the MESSAGE8.5 scenario (climate change is the largest and rapid population growth leads to agricultural expansion), the effect of biodiversity is the worst, which is called the "benchmark scenario".

In the benchmark scenario, it is expected that there will be a serious imbalance in species richness in different regions and countries in 2095. European and North American countries have a high human development index, low biodiversity and widespread historical land transfer, and the species richness of the region will increase significantly by 2095. Economically underdeveloped Southeast Asia, especially in sub-Saharan Africa, is rich in natural biodiversity and more natural and semi-natural habitats, and the region's biodiversity will suffer the most by 2095. Under the AIM6.0 scenario (population increases, urban areas expand, arable land increases, grassland areas decrease sharply, and temperatures rise by 2.5C in 2100), richness in most African countries will increase significantly, while species richness in the Indo-Malaysia region will suffer heavy losses.

It is estimated that the average species richness of grid cells is more than 28.4% lower than that of the benchmark scenario, and the species richness of 41.5% of grid cells will increase by 2095. The article believes that if no action is taken to deal with climate change, it is estimated that by 2100, global richness will continue to decline by 3.4%, with the countries with the most backward economies and the richest biodiversity losing the most. However, this widespread loss of biodiversity is not inevitable. If the whole society takes consistent and strong mitigation measures to deal with climate change and establish a strong carbon trading market, the sustainable development of global biodiversity may be achieved.