Mapping the Impact of Human Activity

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We generally now know that human impact over the last two centuries has meant that virtually every corner of terrestrial ecosystems on Earth has been at least somewhat affected by human activity. While this is true, hope is not lost as recent work has revealed the level of impact is still low in fragile and important ecosystems. Working to conserve these areas and changing how we focus economic activity could stem long-term decline of natural ecosystems.

Different methods have been utilized by landscape ecologists studying the Earth’s relationship to human activity. Measures of human impact include the following maps:  Anthromes, Global Human Modification, Human Footprint, and Low Impact Areas. These all effectively attempt to measure how much human impact has shaped our landmasses. Overall, nearly 50% of the Earth’s terrestrial surfaces has about 20-30%, that is very low impact, and up to 48-56%, or low impact, of measurable human activity. These percentages provide a quantifiable way in demonstrating how much area is changed or altered by land use. Most of these regions that have relatively low or very low impact are in deserts, cold areas such as boreal forests in sub-arctic zones, or remote mountain regions. Three of the four maps agree that 46% of regions without permanent ice have relatively low human impact. All of this suggests that almost half the regions where  people could live and grow food have still low levels of human impact. The more remote deserts and sub-arctic regions generally have even lower, that is very low impact. On the other hand, less than 1% of temperate grasslands, tropical grasslands, mangroves, montane grasslands, tropical coniferous forests, and dry tropical forests have very low human influence across most of the map datasets. These biomes are potentially the most threatened. The study that conducted this assessment indicates that the regions with low impact should be prioritized for conservation efforts, given the potential that human activity could expand in these regions that are habitable or could be exploited by land use activities.[1]

While the study on human impact is revealing and can give us some optimism about the future and also demonstrate where we can focus conservation, other studies have shown that even if human impact is minimal the influence of human activity can be high. For instance, one study showed that different predators react differently not only when human impact was visually evident but even in low impact areas simple human presence can limit or alter animal behaviors. In effect, our influence on the environment can be more than simple direct activities but animal behavior has also learned from human activity and behavior that has altered how fauna responds to the simple presence of humans. To better understand how we affect fauna, we may need new models that can disentangle human activity and human presence to look at how these have temporal and spatial influences on animal behavior.[2] Additionally, another recent study showed that up to half of protected areas showed insignificant differences between their human impact and that of areas outside of them, that is areas not protected. In other words, many protected areas for sensitive biomes are not effective in significantly limiting human activity. Potentially, better governance practices and stronger enforcement measures might be needed to fully protect threatened areas. This also demonstrates that simply protecting areas with relatively low human impact may require strong enforcement measures that ensure protection is likely to be more successful.[3]

Types of human stressors used in the Anthromes, Global Human Modification, Human Footprint and Low Impact Areas datasets.  Figure: Riggio et al., 2020.
Types of human stressors used in the Anthromes, Global Human Modification, Human Footprint and Low Impact Areas datasets. Figure: Riggio et al., 2020.

While conservationists and landscape ecologists have been demonstrating where we could better focus efforts at conservation, economic studies have also attempted to better reorient how national economic policies might be aligned with sustainability targets that promote conservation. For instance, rather than having development goals for countries based on socio-economic measures alone, such as in the human development index (HDI), economists have also used CO2 emissions and material footprint as measures of impact based on activity within a country. The metric measures not only economic and social development, but it is balanced by environmental damage a country is causing. This metric is called the Sustainable Development Index (SDI) that can be used to determine how well countries are balancing economic and policy activities with conservation and environmental protection efforts. The results using this approach show that countries such as Cuba, Costa Rica, and Sri Lanka do relatively well in balancing sustainability and economic goals, while the US and Norway do relatively poorly among rich countries (ranked 159 and 157 respectively). The worst ranked countries are both poor and have a high ecological footprint.[4]

Maps comparing human presence (human detections on camera) and footprint (building density) across the broader landscape between San Jose and Santa Cruz, California.  Maps: Nickel et al., 2020.
Maps comparing human presence (human detections on camera) and footprint (building density) across the broader landscape between San Jose and Santa Cruz, California. Maps: Nickel et al., 2020.

Conservation studies show that there is hope to better conserve regions in many of the Earth’s landmasses in that nearly half these regions still have low or very low human impact. However, other studies show that human impact can go beyond land use activities and that conservation needs far more strict enforcement as protective regions alone may not be sufficient. There also needs to be a balance with economic activity and conservation for many countries and metrics such as the SDI could help to create sustainable targets that also promote improved economic prospects.  

References

[1]    For more on the study that looked at human impact across the Earth using four different measures, see:  Riggio, Jason, Jonathan E. M. Baillie, Steven Brumby, Erle Ellis, Christina M. Kennedy, James R. Oakleaf, Alex Tait, et al. 2020. “Global Human Influence Maps Reveal Clear Opportunities in Conserving Earth’s Remaining Intact Terrestrial Ecosystems.” Global Change Biology, June, gcb.15109. https://doi.org/10.1111/gcb.15109.

[2]    For more on how human activity and human presence can have differential impact on animal behavior, see:  Nickel, Barry A., Justin P. Suraci, Maximilian L. Allen, and Christopher C. Wilmers. 2020. “Human Presence and Human Footprint Have Non-Equivalent Effects on Wildlife Spatiotemporal Habitat Use.” Biological Conservation 241 (January): 108383. https://doi.org/10.1016/j.biocon.2019.108383.


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[3]    For more on how protected areas compared to non-protected areas in terms of human impact, see:  Anderson, Emily, and Christos Mammides. 2019. “The Role of Protected Areas in Mitigating Human Impact in the World’s Last Wilderness Areas.” Ambio 49 (2): 434–41. https://doi.org/10.1007/s13280-019-01213-x.

[4]    For more on the SDI, see:  Hickel, Jason. 2020. “The Sustainable Development Index: Measuring the Ecological Efficiency of Human Development in the Anthropocene.” Ecological Economics 167 (January): 106331. https://doi.org/10.1016/j.ecolecon.2019.05.011.

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