Contemporary Extinction Rate Calculator

Estimate biodiversity loss using the two primary scientific methods.

Species-Area Relationship (SAR)

Red List Rate (E/MSY)

Method 1: Predicting Extinction from Habitat Loss

Method 2: Calculating Rate from Observed Extinctions

Rate vs. Background Rate (1 E/MSY)

Background

Calculated

Chart comparing the calculated extinction rate to the natural background rate.

What are Contemporary Extinction Rates?

Contemporary extinction rates refer to the speed at which species are disappearing in modern times, generally considered to be the period since the Industrial Revolution. These rates are a critical metric for understanding the impact of human activity on global biodiversity. Scientists have determined that current extinction rates are 100 to 1,000 times higher than the natural “background” rate—the rate of extinction before humans became a primary driver of ecosystem change. Understanding these rates is essential for conservation efforts and for assessing the health of our planet. This calculator helps to describe the two methods used to calculate contemporary extinction rates, providing a clearer picture of this ongoing crisis.

The Two Main Methods for Calculating Extinction Rates

Scientists primarily use two different approaches to estimate contemporary extinction rates. One method is projective, based on habitat loss, while the other is reactive, based on observed extinctions.

Method 1: The Species-Area Relationship (SAR) Formula and Explanation

The Species-Area Relationship (SAR) is a predictive model that estimates the number of extinctions based on habitat loss. It’s founded on the ecological principle that larger areas can support a greater number of species. When a habitat is reduced in size, it can no longer support its original number of species, leading to extinctions. While widely used, some argue this method can overestimate extinction.

The formula to find the number of remaining species (S_new) after habitat loss is:

S_new = S_initial * (A_new / A_initial) ^ z

The number of extinctions is then simply the initial number of species minus the new number of species.

Variables for the SAR Method

Variable	Meaning	Unit	Typical Range
S_initial	The starting number of species in the habitat.	Count (unitless)	1 – 1,000,000+
A_new	The remaining area of the habitat after loss.	Area (km², mi², etc.)	Must be less than A_initial
A_initial	The original area of the habitat.	Area (km², mi², etc.)	Greater than 0
z	The extinction coefficient, specific to the ecosystem or taxonomic group.	Unitless	0.15 – 0.35 (common); can vary.

Method 2: Rates from IUCN Red List Data (E/MSY)

This method calculates the extinction rate based on documented extinctions recorded by organizations like the International Union for Conservation of Nature (IUCN). The rate is typically expressed in “Extinctions per Million Species-Years” (E/MSY). This allows for a standardized comparison across different taxonomic groups and time periods. For instance, if 10 species go extinct out of 10,000 species over 100 years, the E/MSY would be 100. This is 100 times the background rate of 1 E/MSY.

The formula is:

E/MSY = (Number of Extinctions / Number of Species) * (1,000,000 / Years)

Variables for the E/MSY Method

Variable	Meaning	Unit	Typical Range
Number of Extinctions	The count of species that have gone extinct in the observation period.	Count (unitless)	0+
Number of Species	The total number of species within the group being assessed.	Count (unitless)	Greater than 0
Years	The time period over which the extinctions were observed.	Time (years)	1 – 500+

Practical Examples

Example 1: SAR Method (Rainforest Deforestation)

• Inputs:
  • Initial Area: 200,000 km²
  • Remaining Area: 100,000 km² (50% loss)
  • Initial Species: 10,000
  • Z-Value: 0.25
• Calculation: S_new = 10,000 * (100,000 / 200,000)^0.25 ≈ 8,409 species.
• Results:
  • Predicted Extinctions: 1,591 species
  • Remaining Species: 8,409
  • Percentage Loss: 15.9%

Example 2: E/MSY Method (Bird Extinctions)

Let’s look at birds, a well-documented group.

• Inputs:
  • Number of Observed Extinctions: 150 (since 1500)
  • Number of Species in Group: ~11,000 (modern bird species)
  • Time Period: ~520 years
• Calculation: E/MSY = (150 / 11,000) * (1,000,000 / 520) ≈ 26.2 E/MSY.
• Result: The contemporary extinction rate for birds is over 26 times the natural background rate.

How to Use This Contemporary Extinction Rate Calculator

Follow these steps to estimate extinction rates:

1. Select the Method: Choose between the ‘Species-Area Relationship (SAR)’ and ‘Red List Rate (E/MSY)’ tabs based on the data you have.
2. Enter Your Data:
   • For SAR, input the initial and final habitat areas, the total number of species, and the Z-value. The Z-value often varies by location; continental areas are typically ~0.25, while islands can be higher.
   • For E/MSY, input the number of recorded extinctions for a specific group, the total number of species in that group, and the time frame in years over which you are measuring.
3. Review the Results: The calculator will automatically show the primary result (predicted extinctions or the E/MSY rate) and key intermediate values. The bar chart provides a visual comparison of the calculated rate to the background rate of 1 E/MSY.
4. Interpret the Output: A high number of predicted extinctions or an E/MSY rate significantly above 1 indicates a severe impact on biodiversity. For more on conservation, you can check out details on {related_keywords}.

Key Factors That Affect Contemporary Extinction Rates

Several interconnected factors, largely driven by human activity, accelerate contemporary extinction rates. Understanding these is crucial when you describe the two methods used to calculate contemporary extinction rates.

• Habitat Loss and Fragmentation: This is the single largest driver of extinction. Agriculture, urbanization, and deforestation destroy and break apart the ecosystems species need to survive. You can learn more about this at {internal_links}.
• Climate Change: Rising temperatures and changing weather patterns alter habitats, forcing species to adapt or move. Those that cannot are at high risk.
• Invasive Species: Introduced predators, competitors, and diseases can decimate native populations that have no natural defenses. This is a primary cause of extinction on islands.
• Pollution: Chemical pollutants from industry and agriculture, as well as plastic waste, can poison ecosystems and harm wildlife directly.
• Overexploitation: Overhunting, overfishing, and poaching for the wildlife trade have driven many species, like the passenger pigeon and dodo, to extinction.
• Disease: Human activities can facilitate the spread of novel diseases to wildlife populations, leading to rapid declines. An example is the chytrid fungus affecting amphibian populations globally.

Frequently Asked Questions (FAQ)

1. What is the “background” rate of extinction?

The background rate is the natural rate of extinction estimated from the fossil record before human influence, typically cited as around 1 extinction per million species-years (1 E/MSY).

2. Which calculation method is more accurate?

Both methods have strengths and weaknesses. The SAR method is a projection and can be sensitive to the Z-value used. The E/MSY method relies on observed data, which can be incomplete, especially for less-studied groups like insects and fungi.

3. Why is the Z-value in the SAR formula important?

The Z-value determines how sensitive species richness is to area changes. A higher Z-value means more species will be lost for the same amount of habitat reduction. It reflects how isolated or unique the species in an area are. For information about species distribution, see {related_keywords}.

4. Does this calculator account for “extinction debt”?

The SAR calculation inherently reflects the concept of extinction debt—the idea that extinctions from habitat loss are not immediate but will occur over time as populations decline. For more on this, visit {internal_links}.

5. Can conservation efforts lower the extinction rate?

Yes. Studies have shown that targeted conservation efforts, such as habitat protection and managing invasive species, can slow and even reverse the decline of threatened species, effectively lowering the realized extinction rate.

6. How does the IUCN Red List relate to these calculations?

The IUCN Red List of Threatened Species is the primary source of data for the E/MSY method. It documents species that are extinct (EX) or extinct in the wild (EW), providing the raw numbers needed for the calculation.

7. Are we in a sixth mass extinction?

Many scientists argue that the current high contemporary extinction rates, driven by human activity, signify the beginning of the Earth’s sixth mass extinction event.

8. What is the difference between Extinct (EX) and Extinct in the Wild (EW)?

An EX species has no living individuals left anywhere. An EW species survives only in captivity or as a naturalized population outside its historic range. Both are used in E/MSY calculations.