Reboisement | EPFL Graph Search

Le reboisement est une opération qui consiste à créer des zones boisées ou des forêts qui ont été supprimées par coupe rase (ou « coupe à blanc ») ou détruites par différentes causes dans le passé (surexploitation, feu de forêt, surpâturage, guerre…). Parfois, il s'agit explicitement de forêts de protection. Le reboisement spontané désigne le stade terminal de la succession des différentes phases de reconquête forestière. L'afforestation est le boisement sur des terres vierges d'arbres depuis longtemps. Les boisements ou massifs forestiers ainsi (re)créés peuvent présenter divers bénéfices tant pour les écosystèmes et en tant qu'aménité, que pour les ressources économiques restaurées. Ce sont aussi potentiellement des puits de carbone (s'ils ne brûlent pas de manière répétée). La notion de « reforestation » laisse supposer un objectif plus ambitieux du point de vue de la surface et de la qualité écologique ou paysagère que celle de reboisement. L'objectif étant alors généraleme

A game-theoretical model of deforestation in human-environment relationships

Antonio Rodrigues

We studied a two-person game regarding deforestation in human–environment relationships. Each landowner manages a single land parcel where the state of land-use is forested, agricultural, or abandoned. The landowner has two strategies available: forest conservation and deforestation. The choice of deforestation provides a high return to the landowner, but it degrades the forest ecosystem services produced on a neighboring land parcel managed by a different landowner. Given spatial interactions between the two landowners, each landowner decides which strategy to choose by comparing the expected discounted utility of each strategy. Expected discounted utility is determined by taking into account the current and future utilities to be received, according to the state transition on the two land parcels. The state transition is described by a Markov chain that incorporates a landowner's choice about whether to deforest and the dynamics of agricultural abandonment and forest regeneration. By considering a stationary distribution of the Markov chain for land-use transitions, we derive explicit conditions for Nash equilibrium. We found that a slow regeneration of forests favors mutual cooperation (forest conservation). As the forest regenerates faster, mutual cooperation transforms to double Nash equilibria (mutual cooperation and mutual defection), and finally mutual defection (deforestation) leads to a unique Nash equilibrium. Two different types of social dilemma emerge in our deforestation game. The stag-hunt dilemma is most likely to occur under an unsustainable resource supply, where forest regenerates extremely slowly but agricultural abandonment happens quite rapidly. In contrast, the prisoner's dilemma is likely under a persistent or circulating supply of resources, where forest regenerates rapidly and agricultural abandonment occurs slowly or rapidly. These results show how humans and the environment mutually shape the dilemma structure in forest management, implying that solutions to dilemmas depend on environmental properties.

2009

Substantial decrease in CO2 emissions from Chinese inland waters due to global change

Tom Ian Battin

Carbon dioxide (CO2) evasion from inland waters is an important component of the global carbon cycle. However, it remains unknown how global change affects CO2 emissions over longer time scales. Here, we present seasonal and annual fluxes of CO2 emissions from streams, rivers, lakes, and reservoirs throughout China and quantify their changes over the past three decades. We found that the CO2 emissions declined from 13831 Tg C yr(-1) in the 1980s to 98 +/- 19 Tg C yr(-1) in the 2010s. Our results suggest that this unexpected decrease was driven by a combination of environmental alterations, including massive conversion of free-flowing rivers to reservoirs and widespread implementation of reforestation programs. Meanwhile, we found increasing CO2 emissions from the Tibetan Plateau inland waters, likely attributable to increased terrestrial deliveries of organic carbon and expanded surface area due to climate change. We suggest that the CO2 emissions from Chinese inland waters have greatly offset the terrestrial carbon sink and are therefore a key component of China's carbon budget. Inland waters emit greenhouse gases, but robust estimations are hampered by a dearth of spatio-temporally resolved measurements. Here the authors present annual fluxes of CO2 from Chinese inland waters over the past several decades, showing that emission fluxes have significantly declined since the 80s.

NATURE RESEARCH2021

Pre-Columbian deforestation as an amplifier of drought in Mesoamerica

Jed Oliver Kaplan

Droughts in pre-Columbian Mesoamerica caused significant societal disruptions during the Late Classic and Post-Classic Periods. While the primary causes of these droughts are still debated, it has been speculated that they may be linked to extensive deforestation associated with high population densities during these intervals. Here we show that pre-Columbian deforestation would have biased the climate in Mesoamerica towards a drier mean state, amplifying drought in the region. In climate model simulations using a pre-Columbian land cover reconstruction, annual precipitation decreases by 5%-15% throughout southern Mexico and the Yucatan compared to simulations using either natural forest cover or forest regrowth associated with population declines after 1500 C. E. These changes are driven primarily by large reductions (10%-20%) in precipitation during the late summer wet season (August-September). When compared to precipitation changes estimated to have occurred during the Maya collapse, our results suggest that deforestation could account for up to sixty percent of the mean drying during this interval. Many regions previously deforested in the pre-Columbian era are now under dense forest cover, indicating potential future climate impacts should tropical deforestation of these areas accelerate. Citation: Cook, B. I., K. J. Anchukaitis, J. O. Kaplan, M. J. Puma, M. Kelley, and D. Gueyffier (2012), Pre-Columbian deforestation as an amplifier of drought in Mesoamerica, Geophys. Res. Lett., 39, L16706, doi:10.1029/2012GL052565.

Amer Geophysical Union2012

A game-theoretical model of deforestation in human-environment relationships

Antonio Rodrigues

2009