Biodiversity is globally declining due to anthropogenic activities and climate change. According to Treweek et al. (2006), the rate of global diversity loss has been faster in the past 50 years than at any other time in human history. The 2020 Living Planet Report, released by the World Wildlife Fund (WWF), reveals an average 68% drop in populations of mammals, birds, fish, reptiles, and amphibians since 1970. According to the International Union for Conservation of Nature (IUCN) (2021), over 40,000 species (28% of all species assessed) are currently threatened with extinction, with this number continuing to rise.
WWF (2018) identified five key threats to biodiversity:
- Habitat loss and degradation
- Species overexploitation
- Pollution
- Invasive species and disease
- Climate change.
According to Hogue and Breon (2022), habitat loss and degradation pose the most significant threat to biodiversity, endangering more species than all other categories combined. This trend is expected to continue, as an increasing number of natural habitats are destroyed or transformed into anthropogenic landscapes. Therefore, habitat loss and degradation will remain the primary concern in biodiversity conservation efforts. According to WWF (2018, p. 74), the most common causes of habitat loss and degradation are “unsustainable agriculture, logging, transportation, residential or commercial development, energy production and mining.”
Species overexploitation occurs when certain populations of a species are harvested at a faster rate than they can be replenished. This practice can lead to extinction at the population level or even the species level.
- The overexploitation of aquatic species, commonly known as overfishing, has resulted in significant losses in aquatic biodiversity. The Atlantic bluefin tuna is a prime example of an aquatic species that has been driven close to extinction due to overfishing. This species, a favorite among fishermen and sushi lovers, has been caught at a much faster rate than it can reproduce, resulting in a sharp decline in its population. Today, the total stock of Atlantic bluefin tuna is only 13% of its levels 70 years ago.
Many other aquatic species are facing similar challenges to the Atlantic bluefin tuna. According to Roberson et al. (2020), over 90 endangered fish and invertebrate species are being caught in industrial fisheries, which account for 99% of the catch volume and value of these species. - Overexploitation of terrestrial animals and plant species also occurs in many regions of the world, although to a lesser extent than aquatic species. For instance, Bodeker et al. (2014) investigated the overexploitation of Prunus africana Kalkman, a medicinal plant valued for its anti-inflammatory and analgesic properties. The plant’s overharvesting in the 1990s resulted in a severe depletion of its stock, which also had an indirect impact on other species, as the plant ‘provides habitat and food for endemic birds, rare primates, insects, and nonvascular canopy epiphytes such as orchids, ferns, and mosses’ (Bodeker et al., 2014, 811).
Pollution
Pollution, including from chemicals, fossil fuels, and plastics, is widely recognized as a significant driver of biodiversity loss. Arellano et al. (2017) provided evidence of reduced plant diversity and richness resulting from petroleum pollution in the Ecuadorian Amazon. Azevedo-Santos et al. (2021) investigated plastic pollution in freshwater ecosystems worldwide and found evidence of plastic ingestion by 206 freshwater species, including numerous invertebrates, fish, and mammal species.
Invasive species and disease
Invasive species are organisms that cause ecological damage in new environments where they are not native. Invasive species pose severe threats to native organisms by competing with them for limited resources and altering their habitats, which can lead to their extinctions.
Climate change
Climate change can have a negative impact on biodiversity by altering the environments where many species live. For instance, sea-level rise (SLR) is primarily caused by two factors related to global warming: the increased volume of seawater due to the melting of ice sheets and glaciers and the expansion of seawater as it warms (NASA, 2022). SLR is expected to result in a significant loss of coastal and island biodiversity (Allen and Lendemer, 2016). According to a groundbreaking report from the Center for Biological Diversity, 233 threatened and endangered species in 23 coastal US states are at risk from SLR, which could severely threaten the survival of 17% of federally protected species.
References
Allen, J. L., & Lendemer, J. C. (2016). Quantifying the impacts of sea-level rise on coastal biodiversity: A case study on lichens in the mid-Atlantic Coast of eastern North America. Biological Conservation, 202, 119–126.
Arellano, P., Tansey, K., Balzter, H., & Tellkamp, M. (2017). Plant Family-Specific Impacts of Petroleum Pollution on Biodiversity and Leaf Chlorophyll Content in the Amazon Rainforest of Ecuador. PLoS ONE, 12(1), 1–18.
Azevedo-Santos, V. M., Brito, M. F. G., Manoel, P. S., et al. (2021). Plastic pollution: A focus on freshwater biodiversity. AMBIO – A Journal of the Human Environment, 50(7), 1313–1324.
Bodeker, G., van ’t Klooster, C., & Weisbord, E. (2014). Prunus africana (Hook.f.) Kalkman: The Overexploitation of a Medicinal Plant Species and Its Legal Context. Journal of Alternative & Complementary Medicine, 20(11), 810–822.
International Union for Conservation of Nature. (2021). The IUCN red list of threatened species. Version 2021-1. IUCN. Retrieved from www.iucnredlist.org
NASA, 2022. https://climate.nasa.gov/vital-signs/sea-level/
Roberson, L. A., Watson, R. A., & Klein, C. J. (2020). Over 90 endangered fish and invertebrates are caught in industrial fisheries. Nature communications, 11(1), 4764. https://doi.org/10.1038/s41467-020-18505-6
Treweek, J. R. , Brown, C. & Bubb, P. (2006). Assessing biodiversity impacts of trade: a review of challenges in the agriculture sector. Impact Assessment and Project Appraisal, 24 (4), 299-309. https://doi.org/10.3152/147154606781765057
WWF. (2018). Living planet report: 2018: Aiming higher. Retrieved from https://www.worldwildlife.org/pages/living-planet-report-2018
WWF. (2020). Living planet report. Retrieved from https://livingplanet.panda.org/en-us/
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