The latter phenomenon can be temporary or permanent, depending on whether the environmental degradation that leads to the loss is reversible through ecological restoration / ecological resilience or effectively permanent (e.g. through land loss). Global extinction has so far been proven to be irreversible.
Even though permanent global species loss is a more dramatic phenomenon than regional changes in species composition, even minor changes from a healthy stable state can have dramatic influence on the food web and the food chain insofar as reductions in only one species can adversely affect the entire chain (coextinction), leading to an overall reduction in biodiversity, possible alternative stable states of an ecosystem notwithstanding. Ecological effects of biodiversity are usually counteracted by its loss. Reduced biodiversity in particular leads to reduced ecosystem services and eventually poses an immediate danger for food security, also for humankind.
Locally bounded loss rates can be measured using species richness and its variation over time. Raw counts may not be as ecologically relevant as relative or absolute abundances. Taking into account the relative frequencies, a considerable number of biodiversity indexes has been developed. Besides richness, evenness and heterogeneity are considered to be the main dimensions along which diversity can be measured.
As with all diversity measures, it is essential to accurately classify the spatial and temporal scope of the observation. "Definitions tend to become less precise as the complexity of the subject increases and the associated spatial and temporal scales widen. Biodiversity itself is not a single concept but can be split up into various scales (e.g. ecosystem diversity vs. habitat diversity or even biodiversity vs. habitat d.) or different subcategories (e.g. phylogenetic diversity, species diversity, genetic diversity, nucleotide diversity). The question of net loss in confined regions is often a matter of debate but longer observation times are generally thought to be beneficial to loss estimates.
To compare rates between different geographic regions latitudinal gradients in species diversity should also be considered.
- Habitat loss and degradation
- Climate change through heat stress and drought stress
- Excessive nutrient load and other forms of pollution
- Over-exploitation and unsustainable use (e.g. unsustainable fishing methods) we are currently using 25% more natural resources than the planet
- Invasive alien species that effectively compete for a niche, replacing indigenous species
In 2017, various publications describe the dramatic reduction in absolute insect biomass and number of species in Germany and North America over a period of 27 years. As possible reasons for the decline, the authors highlight neonicotinoids and other agrochemicals. Writing in the journal PLOS One, authors Hallman, Sorg, et al (2017), conclude that "the widespread insect biomass decline is alarming."
- Cardinale, Bradley; et al. (2012). "Biodiversity loss and its impact on humanity". Nature. 486 (7401): 59–67. Bibcode:2012Natur.486...59C. doi:10.1038/nature11148. PMID 22678280.
...at the first Earth Summit, the vast majority of the world’s nations declared that human actions were dismantling the Earth’s ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.
- "Biological diversity and habitat diversity: a matter of Science and perception" (PDF).
- "Estimating local biodiversity change: a critique of papers claiming no net loss of local diversity". Ecology. 97 (8): 1949–1960. 2016. doi:10.1890/15-1759.1.
two recent data meta-analyses have found that species richness is decreasing in some locations and is increasing in others. When these trends are combined, these papers argued there has been no net change in species richness, and suggested this pattern is globally representative of biodiversity change at local scales
- Bradley Cardinale. "Overlooked local biodiversity loss (letter and response)".
- "Global Biodiversity Outlook 3". Convention on Biological Diversity. 2010.
- "Land use intensification alters ecosystem multifunctionality via loss of biodiversity and changes to functional composition". Ecol Lett. 18 (8): 834–843. 2015. doi:10.1111/ele.12469. PMC .
- Walsh JR1, Carpenter SR, Vander Zanden MJ. (2016). "Invasive species triggers a massive loss of ecosystem services through a trophic cascade". Proc Natl Acad Sci U S A. 13 (15): 4081–5. doi:10.1073/pnas.1600366113. PMC .
- Dicks, Lynn V.; Viana, Blandina; Bommarco, Riccardo; Brosi, Berry; Arizmendi, María del Coro; Cunningham, Saul A.; Galetto, Leonardo; Hill, Rosemary; Lopes, Ariadna V.; Pires, Carmen; Taki, Hisatomo; Potts, Simon G. (2016-11-25). "Ten policies for pollinators". Science. 354 (6315): 975–976. doi:10.1126/science.aai9226. ISSN 0036-8075. PMID 27884996. Retrieved 2017-10-20.
- "Where have all the insects gone?". Science | AAAS. 2017-05-09. Retrieved 2017-10-20.
- Hallmann, Caspar A.; Sorg, Martin; Jongejans, Eelke; Siepel, Henk; Hofland, Nick; Schwan, Heinz; Stenmans, Werner; Müller, Andreas; Sumser, Hubert; Hörren, Thomas; Goulson, Dave; de Kroon, Hans (2017-10-18). Lamb, Eric Gordon, ed. "More than 75 percent decline over 27 years in total flying insect biomass in protected areas". PLOS ONE. Public Library of Science (PLoS). 12 (10): e0185809. doi:10.1371/journal.pone.0185809. ISSN 1932-6203.
- Anup Shah (2014). "Loss of Biodiversity and Extinctions". globalissues.org.
- "How does Biodiversity loss affect me and everyone else?". panda.org.
- "TOPICS IN BIODIVERSITY LOSS". Global Change Project of the Paleontological Research Institution.
- Charles Perrings (2008). Biodiversity Loss: Economic and Ecological Issues. Cambridge University Press. ISBN 978-0521588669.
- Neil Griffin, ed. (2015). Biodiversity Loss in the 21st Century. Ml Books International - Ips. ISBN 978-1632390943.
- Alexander Wood (2000). The Root Causes of Biodiversity Loss. Routledge. ISBN 978-1853836992.