IPBES/6/INF/1/Rev.1 Chapter 4 Status and trends of land degradation and restoration and associated changes in biodiversity and ecosystem functions Coordinating Lead Authors Stephen Prince (United States of America), Graham Von Maltitz (South Africa), Fengchun Zhang (China) Lead Authors Kenneth Byrne (Ireland), Charles Driscoll (United States of America), Gil Eshel (Israel), German Kust (Russian Federation), Cristina Martínez-Garza (Mexico), Jean Paul Metzger (Brazil), Guy Midgley (South Africa), David Moreno Mateos (Spain), Mongi Sghaier (Tunisia/OSS), San Thwin (Myanmar) Fellow Bernard Nuoleyeng Baatuuwie (Ghana) Contributing Authors Albert Bleeker (the Netherlands), Molly E. Brown (United States of America), Leilei Cheng (China), Kirsten Dales (Canada), Evan Andrew Ellicot (United States of America), Geraldo Wilson Fernandes (Brazil), Violette Geissen (the Netherlands), Panu Halme (Finland), Jim Harris (United Kingdom of Great Britain and Northern Ireland), Roberto Cesar Izaurralde (United States of America), Robert Jandl (Austria), Gensuo Jia (China), Guo Li (China), Richard Lindsay (United Kingdom of Great Britain and Northern Ireland), Giuseppe Molinario (United States of America), Mohamed Neffati (Tunisia), Margaret Palmer (United States of America), John Parrotta (United States of America), Gary Pierzynski (United States of America), Tobias Plieninger (Germany), Pascal Podwojewski (France), Bernardo Dourado Ranieri (Brazil), Mahesh Sankaran (India), Robert Scholes (South Africa), Kate Tully (United States of America), Ernesto F. Viglizzo (Argentina), Fei Wang (China), Nengwen Xiao (China), Qing Ying (China), Caiyun Zhao (China) Review Editors Chencho Norbu (Bhutan), Jim Reynolds (United States of America) This chapter should be cited as: Prince, S., Von Maltitz, G., Zhang, F., Byrne, K., Driscoll, C., Eshel, G., Kust, G., Martínez-Garza, C., Metzger, J. P., Midgley, G., Moreno-Mateos, D., Sghaier, M., and Thwin, S. Chapter 4: Status and trends of land degradation and restoration and associated changes in biodiversity and ecosystem fundtions. In IPBES (2018): The IPBES assessment report on land degradation and restoration. Montanarella, L., Scholes, R., and Brainich, A. (eds.). Secretariat of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem services, Bonn, Germany, pp. xx-xx. 315 IPBES/6/INF/1/Rev.1 Executive Summary ............................................................................................................ 317 4.1 Introduction ................................................................................................................ 321 4.1.1 Aims ............................................................................................................................................ 321 4.1.2. The degradation process ............................................................................................................ 322 4.1.3 Detection of degradation ............................................................................................................ 326 4.1.4 Baselines ..................................................................................................................................... 328 4.1.5 Future trends of degradation ...................................................................................................... 332 4.1.6 History of degradation studies .................................................................................................... 334 4.2 Individual degradation processes ................................................................................. 335 4.2.1 Soil erosion .................................................................................................................................. 335 4.2.2 Loss of soil fertility ...................................................................................................................... 340 4.2.3 Changes in carbon stocks following degradation and restoration.............................................. 344 4.2.4 Pollution ...................................................................................................................................... 351 4.2.5 Changes in the hydrological regime ............................................................................................ 361 4.2.6 Changes in land cover ................................................................................................................. 366 4.2.7 Pests and diseases ...................................................................................................................... 384 4.2.8 Climate Change impacts.............................................................................................................. 386 4.2.9 Biodiversity Loss .......................................................................................................................... 391 4.3 Degradation impacts in response to human drivers....................................................... 397 4.3.1 Native habitat loss ...................................................................................................................... 397 4.3.2 Grazing land degradation ............................................................................................................ 399 4.3.3 Cropping Systems ........................................................................................................................ 401 4.3.4 Forest degradation ...................................................................................................................... 402 4.3.5 Non-timber forest use: woodfuel, bushmeat, edible plants, and medicinal herbs .................... 407 4.3.6 Changes in fire regimes ............................................................................................................... 408 4.3.7 Invasive species ........................................................................................................................... 410 4.3.8 Land abandonment ..................................................................................................................... 414 4.3.9 Mining ......................................................................................................................................... 415 4.3.10 Infrastructure, industry, urbanization ....................................................................................... 418 4.4 The way forward .......................................................................................................... 421 4.4.1 Status of biophysical knowledge of land degradation ................................................................ 421 4.4.2 Gaps in understanding of processes of degradation .................................................................. 422 4.4.3 Measurement, monitoring and trend detection ......................................................................... 424 References ......................................................................................................................... 426 316 IPBES/6/INF/1/Rev.1 Executive Summary There is wide consensus that land degradation is a global phenomenon resulting in a substantial loss of both biodiversity and ecosystem services (well established). However, the global extent, severity and trends in degradation remain inconclusive. The negative impact of degradation on ecosystem services has been well established in numerous local studies. Often quoted figures suggest that four-fifths of agricultural land suffers from severe erosion, as do 10-20% of rangelands {4.1.6, 4.2.6.2}. These numbers are, however, inconclusive, mostly dated and hard to verify {4.1.6}. Many global studies focus on single, narrowly-focused indicators and do not account for the multiple forms of degradation, all of which reduce biodiversity and ecosystem services. In the case of wetlands, an estimated 75% have been lost (established but incomplete) {4.2.5.2}. The extent and rate of forest loss is well established, but condition changes within forests are poorly resolved {4.3.1, 4.3.4}. Degradation is occurring in all land-cover, land-use and landscape types and in all countries (well established). This results in a loss of biodiversity {4.2.9} and ecosystem services through: the loss of forests {4.3.4}, rangelands {4.3.2} and wetlands {4.2.5.2}; increased erosion {4.1.1} resulting in reduced net primary production {4.2.3} and crop yields {4.3.3}; increases in destructive wildfires {4.3.6}, sometimes exacerbated by invasive alien plants {4.3.7}; increases in outbreaks of pests and diseases causing losses to natural and crop fauna and flora {4.2.7}; changes in forage quality {4.2.6.2}; and the loss of regulating services such as carbon sequestration {4.2.3} and hydrological function {4.2.5}. Degradation takes place through a number of biophysical processes and can manifest itself in a wide variety of ways (well established). A single direct driver of degradation may affect a multitude of degradation processes, often through a cascading set of interactions {4.1.2}. For instance, removal of vegetation through overgrazing may exacerbate soil erosion, losses of soil organisms and soil organic matter. In combination, these impacts change soil fertility, water infiltration and the water-holding capacity of the soil. The combined effect leads to reduced net primary production, loss of biodiversity and reduced resilience of the landscape when environmental changes occur. Some impacts, such as