The terrestrial biosphere has been altered by human activity
For over a century, researchers have been exploring global-scale relationships between climate and terrestrial ecosystems. Many simple but effective models have been developed to understand and map vegetation as conditioned by climate and other environmental factors. One of the most successful schemes is the Holdridge Life Zone system (see figure below), where biomes are classified based on broad correlations between precipitation, temperature and elevation. Originally published in 1947, variants of the Holdridge Life Zone system continue to play a key role in global studies of the interactions of climate and natural resources: recent examples include studies on the conservation of dry forests, the effects of climate change on terrestrial aridity, and the mapping of land degradation risk.
However, there is a compelling argument that “It is no longer possible to understand, predict, or successfully manage ecological pattern, process, or change without understanding why and how humans reshape these over the long term”. Hence, the concept of anthromes or “anthropogenic biomes”) was introduced to acknowledge that the majority of the terrestrial biosphere of the Earth has been altered by human activity. We are now living in the Anthropocene where, both intentionally and unintentionally, humans are global-scale ecosystem engineers.
Anthromes are global ecological patterns created by the sustained interactions between humans and ecosystems. As illustrated in the previous pages of this atlas, human domination of the planet is extensive and is the main driver of global environmental change. The concept of anthromes and their global mapping encourages a rethinking of the biosphere since it “puts people in the map,” which reveals the geographical extent and functional depth of human impacts. The current distribution and types of anthromes represents an integration of the long period of time it took to develop and expand agriculture (over the past 10 000 years) with human population growth and dispersion across the globe.
Human impacts – and their disruption of ecosystem structure, processes and services – include both high- and low-intensive disturbances. Examples include urbanisation, infrastructure (roads, boreholes, pipelines, sewage systems, electricity lines, etc.), extraction (e.g. mining, fracking, logging, dredging, and groundwater loss), agriculture (e.g. cultivation, irrigation, landless livestock systems, land clearing, salinisation), various types of pollution (oil spills, heavymetal contamination, pesticides, medical waste, etc.), garbage spills, and livestock grazing.
The direct and indirect consequences of any disturbance at any point on the Earth will vary, depending on the complex interactions of three factors: (a) biophysical conditions (soil fertility, elevation, biome type, climate, water availability, infrastructure, etc.), (b) social characteristics (cultural traditions and practices, population density, gender equality, political stability, etc.), and (c) economic state (proximity and access to markets, regulatory constraints, degree of wealth, dependency on state institutions, diversification of market products, etc.). Elucidating the specific consequences of these disturbances at tens of thousands of locales across the planet is key to ultimately understanding the complex diversity of relationships between humans and ecosystems.
Holdridge Life Zone Classification scheme. Potential evapotranspiration is the amount of evaporation that would occur if water were not limited. Annual precipitation is rain or snow.
Source: Halasz, P., 2007 [CC BY-SA].
Long-term global changes in:
(A) major categories of sociocultural systems,
(B) historical estimates of human population and
(C) anthropogenic transformation of the terrestrial biosphere.
Arrows indicate that Paleolithic to Neolithic transitions are regional, not global. Time scale prior to 1900 is logarithmic years BP, after 1900 are calendar years.
Source: E.C. Ellis, 2015.