#Hemispheric defense zone date free#

The start of the Anthropocene is open to debate ( 3) with some arguments for a start at the dawn of agriculture (5,000–10,000 years ago) or even with the Pleistocene megafaunal extinctions 10,000–50,000 years ago, but its start is frequently ascribed to the early Industrial Revolution (∼1800) or to the start of the Great Acceleration (∼1950). Some key features of the Anthropocene include recognition that ( a) human-altered processes are of comparable magnitude to natural processes in many aspects of the global biosphere ( b) human influence has multiple dimensions, and this influence is occurring at scales ranging from local to global ( c) there has been a pronounced surge in human influence and the pace of change since the mid-twentieth century, the so-called Great Acceleration ( sensu 2), which is continuing and expanding in the twenty-first century (see also the sidebar, When Did the Anthropocene Begin?) ( d) the magnitude and spatial scale of change may reach tipping points and regional or planetary boundaries, which will result in major shifts in Earth system functioning when passed and ( e) the degree of human influence is such that shifts in ecosystem function and the emergence of increasingly altered ecosystems are likely to be occurring in even the most remote and protected regions. This term has recently gained widespread usage as a descriptor of the current state of the planet. The growing scale and intensity of our influence have modified the functioning of the Earth system, leading to the suggestion that Earth has entered a new geological epoch, the Anthropocene ( 1, 2).

#Hemispheric defense zone date free#

Human influence on the planet and its functioning is all-pervasive and spreading, such that no biome of Earth's surface is free from interactions with humanity. We highlight the importance of this understanding to develop the strategies necessary for shaping the transition of tropical forests through the early Anthropocene, as well as highlight the opportunities and challenges for the tropical forest science community in the coming decades. As a consequence, most tropical forests are on a trajectory to becoming altered ecosystems, with the degree of alteration dependent on the intensity and duration of the current bottleneck of human-induced pressures. The patterns of change are spatially heterogeneous, are often characterized by strong interactions among different drivers, can have both large-scale and remote effects, and can play out through ecological cascades over long timescales. Key facets include deforestation driven by agricultural expansion, timber and wood extraction, the loss of fauna that maintain critical ecological connections, the spread of fire, landscape fragmentation, the spread of second-growth forests, new species invasion and pathogen spread, increasing CO 2, and climate change. Here, we review and synthesize our understanding of Anthropocene changes in tropical forests.

The Anthropocene is characterized as an epoch when human influence has begun to fundamentally alter many aspects of the Earth system and many of the planet's biomes.