Nature loss is the fastest emerging business governance issue of the 2020s. A decline in biodiversity due to human activity is affecting the essential ecosystem services we rely upon, such as food production and flood control. Nature change is systemic but locally unique, so it is changing everywhere, differently, presenting a labyrinthine risk to humanity.
8 min read | Last updated 22 March 2021
The WWF and Zoological Society of London’s biennial Living Planet Report 2020 (pdf) is a disturbing read, alerting us to significant loss of biodiversity around the world over the last 50 years. Monitored populations of wildlife across 4.392 vertebrate species dropped by 68% on average from 1970 to 2016, with freshwater vertebrates dropping by 84%.
The International Union for Conservation of Nature (IUCN) calculates that threatened species span 63% of cycads, 40% of amphibians, 38% of dicots; 34% of reptiles, 34% of conifers; 33% of sharks; 33% of corals; 28% of crustaceans; 26% of mammals, 14% of birds; and 6% of bony fish (IUCN, 2020). It is believed that up to one million plant and animal species face extinction within decades (Nature, 2019).
The decline in New Zealand’s plants, animals and ecosystems on land, in fresh water and at sea is set out in the Department of Conservation report Biodiversity in Aotearoa, 2020 (pdf).
- major decline or extinction in many indigenous land-based species is due to a reduction in the extent and quality of natural habitats, introduced predators and herbivores and legacy impacts (eg harvesting)
- indigenous vegetation losses continue with land-use change and intensification, and less than half of land area remains in indigenous vegetation cover
- of terrestrial species assessed, 7% are threatened and 22% are at risk
- conservation management has improved the conservation status of 23 land bird species
- New Zealand has more than 425,000 km of mapped rivers and streams, 50,000 lakes, geothermal and cold-water springs, karst systems and 200 identified aquifers
- wetland ecosystems have declined by 90% since people arrived
- habitats and species are suffering increased sedimentation, eutrophication and other physical damage as a result of increased agricultural activities and urbanisation
- of freshwater species assessed, 14% are threatened and 17% are at risk
- New Zealand has 15 times more sea than land area
- habitats include sheltered inlets, fiords, estuaries, seagrass beds, rimurapa/kelp forests, shellfish beds, hydrothermal vents, extensive sandy coasts through to rocky coasts and reefs and the open ocean
- pressures include climate change, harvesting and pollution
- of marine species, over half are endemic, and of those assessed, 4% are threatened and 32% are at risk
We don’t know how many species there are on Earth (estimates vary from five million to one trillion). About 1.6 million species have so far been described, with about 18,000 new species being added to the register each year. We know enough about rates of change among known species to be very concerned about loss of biodiversity across all species, known and unknown.
Biodiversity is a measure of variety in ecosystems, defined in two ways:
- Genetic diversity, the number of different species in an area
- Functional diversity, the value and range of species traits that influence a particular ecosystem’s functioning
Loss of biodiversity is the rate at which species are being lost from ecosystems, indicated by:
- Global extinctions (which are irreversible)
- Local extinction or endangerment of species (which can be reversible)
Extinction is natural. The background rate of extinctions is debated between academics, but is somewhere between 0.1 and 2 extinctions per million species per year (E/MSY); if there were, say, 10 million species, there would normally be between 1 and 20 extinctions per year.
The opposite of extinction is speciation, the formation of a new species by splitting genetic lineage into two or more new branches. Speciation is highly variable. Some clades (groups of species descended from a common ancestor) are richer than others; for example, there are estimated to be 1.3 million Arthropoda species, but there is only one known Ginkgoaceae species.
The rate of diversification is the net balance of speciation and extinction over time (Scholl and Wien, 2014). Biodiversity increases when speciation exceeds extinction and decreases when extinction exceeds speciation. Generally, the overall rate of speciation is ever so slightly higher than the overall rate of extinction, leading to a very gradual increase in global biodiversity over millions of years. Over Earth’s history, this gentle, general rise has been punctuated by several extraordinary mass extinction events.
In a mass extinction event, biodiversity reduces by at least three quarters in less than three million years. We know of five mass extinction events in Earth’s history. There isn’t yet academic consensus on their causes, but large scale volcanism is associated with the first four events and bolide (meteor) impact is associated with the fifth. These probably resulted in a combination of ocean acidification, metal poisoning, acid rain, ozone damage, darkness, cooling and photosynthetic shutdown, resulting in a massive loss of life. Some 440 million years ago, 85% of life was lost; 374 mya, 75% of life was lost; 250 mya, 95% of life was lost; 200 mya, 80% of life was lost; and 66 mya, 70% of life was lost (including the dinosaurs) (Bond and Grasby, 2017).
Some scientists believe a sixth mass extinction event has begun. Certainly, current extinction rates are higher than would be expected from the fossil record (Barnosky et al, 2011), but estimates of extinction rates vary (Yale Environment 360, 2015). The current rate of extinction for vertebrates (which, it should be noted, constitute less than 2% of species) is thought to be particularly high; somewhere between 100 times (Ceballos et al, 2015) and 1000 times (De Vos et al, 2015) higher than the background rate.
Some researchers dispute that species extinction is as high as is suggested by such studies that extrapolate data based on a species-area relationship (Stork, 2009). Others are not convinced that a sixth mass extinction has begun, but do accept that it is a ‘plausible’ scenario and note that we are at risk of locking in future extinctions if we fail to act now on critical extinction drivers (Barnosky, 2015).
Whatever the extinction rate, it is the loss of abundance that is our call to action, since many species that are not extinct are at risk, surviving in remnant populations that ‘constitute our greatest conservation problem’ but could still be rescued if the public was sufficiently interested (Briggs, 2017).
Loss of a species can disrupt ecosystem stability, leading to co-losses of other species through a trophic (food web) cascade, and may cause ecosystem regime shift (a sudden, persistent change in structure and function). Exploitation of keystone species and apex consumers is particularly impactful on the environment. A keystone species is one that has a disproportionately large effect on its natural environment relative to its abundance, making them critical to their ecosystem community. When wolves in Yellowstone Park were hunted to local extinction in the 1930s, the animals they had preyed on, such as elk and deer, thrived and their grazing destroyed plant life along riverbanks, leading to erosion and a decline in birds, which in turn led to an increase in insects. When wolves were reintroduced, this process reversed. Apex consumers occupy the top trophic level of an ecosystem, with few or no natural predators. Examples include elephants, lions, sea otters, foxes, wolves, bears and rabbits. They affect the population dynamics of the species they consume. Removing or introducing an apex predator can profoundly affect an ecosystem, leading to changes in the incidence of wildfires, the spread of diseases, soil nutrition, water pollution, invasive species and biodiversity (Estes et al, 2011).
Species’ traits influence ecosystem functions and services:
- Ecosystem functions are the processes that regulate the flux of energy and matter through the environment (ie biological growth, nutrient recycling, decomposition)
- Ecosystem services are the benefits of an ecosystem to humans, including provisioning services (eg food, wood and water) and regulating services (eg pest control, flood control and climate regulation), as well as cultural services (eg recreation)
The links between species’ traits, ecosystem functioning and ecosystem services are complex: a trait may influence several services and a service may be influenced by several traits (Laureto et al, 2015). More research is required into how biodiversity affects ecosystem services. We don’t know, for instance, if a forest can store more carbon if it has a greater variety of tree species. More research is also needed in order to develop predictive models that forecast changes in ecosystem services at scale (Cardinale et al, 2014 (pdf)).
Humanity is in trouble if biodiversity declines. Biosphere integrity is one of nine essential Earth systems included in the Planetary Boundaries Framework (below). This framework uses a key indicator to simplify the status of each Earth system in relation to human safety. The key indicator for genetic diversity is extinctions per million species years. Assuming a background rate of 1 E/MSY, a human safety threshold of 10 E/MSY and a current rate of loss of genetic diversity of 100 to 1000 E/MSY for vertebrates, loss of biodiversity is judged to pose a certain, high risk to humanity.
Functional diversity is also an important way of examining biodiversity locally but has not yet been quantified globally. Thus, it is included but not yet quantified in the Planetary Boundaries Framework (Steffen et al, 2015).
Nature loss, ultimately, affects humans.
- We suffer resource shortages. Biodiversity decline reduces the efficacy of the ecosystem services we rely upon, such as flood control, water and air quality and food production. Currently, 821 million people face food insecurity in Asia and Africa, and 11% of all people are undernourished, while 40% of all people lack access to clean drinking water. Resource shortages lead to conflict and refugeeism – there are currently more than 2,500 conflicts over fossil fuels, water, food and land.
- We have to spend more money. Nature loss and fighting nature change drivers depletes budgets that could be spent on other needs, such as education and infrastructure. Due to overexploitation of their ecosystems, low income countries forego an estimated $7 billion to $12 billion in potential fiscal revenues per year, and spend considerable sums trying to combat illegal activities. The US EPA estimates that harmful algal blooms and eutrophication cost the US economy US$2.2–4.6 billion each year (Hudnell 2010). The economic costs of invasive plants and animals are estimated at US$137 billion in the US and iUS$ 33.5 billion in SE Asia per annum, equating to 5% of global GDP in 2011, while climate change cost 2% of global GDP (UNEP, 2016).
- We jeopardise our health. Species loss reduces our options for future discovery of new medicines since 70% of cancer drugs are natural or inspired by nature and nearly all antibiotics are derived from microbes. Meanwhile, nature change increases our exposure to vector-borne diseases, which account for 17% of all infectious diseases and cause 700,000 deaths globally per annum. Plastic microparticles and nanoparticles have entered the food chain and can pass between mother and infant, while studies indicate links between nitrates ingested through drinking water and colorectal cancer, thyroid disease and neural tube defects (Ward et al, 2018).