Table of Contents
Why Record Biological Diversity?
Biological diversity (biodiversity) describes the variety of life: different species, their genetic variation, and the ecosystems they form. In this chapter, the focus is not on what biodiversity is, but on how people have tried to describe, name, and systematically record this diversity over time.
Recording biological diversity serves several purposes:
- Making sense of the enormous variety of organisms
- Enabling communication about organisms across languages and regions
- Providing a foundation for research on evolution, ecology, and conservation
- Allowing comparisons over time (e.g. to detect extinctions or invasions)
Earlier chapters in this section deal with the general historical development of biology; here, we concentrate specifically on the development of methods and ideas for recording diversity.
From Descriptions to Systematic Ordering
Early approaches: descriptive and practical
Long before biology became a science, humans noticed differences among living things. Early recording of diversity was:
- Local and practical: farmers, healers, and hunters distinguished useful and harmful species.
- Descriptive: organisms were often named based on features like color, shape, use, or habitat.
- Non-standardized: the same organism could have many different names; different organisms could share a name.
Lists of medicinal plants, crops, and domestic animals, as well as depictions in art, are early forms of documenting diversity, but they lacked a consistent system.
From “lumping” to “splitting”
As more regions of the Earth were explored:
- New organisms were discovered and drawn or described in travel reports.
- Naturalists began to compare organisms from different continents.
- People realized that vague or purely local naming systems were no longer sufficient.
This led to two opposite tendencies:
- Lumping: grouping different-looking organisms together if considered "similar enough".
- Splitting: recognizing many separate species based on even small differences.
The need for clearer, more consistent criteria for grouping life forms became obvious.
The Birth of Systematics and Taxonomy
The attempt to record diversity in a structured way led to the development of systematics and taxonomy.
- Systematics aims to organize organisms into groups (taxa) and arrange these groups in a system.
- Taxonomy focuses on describing, naming, and classifying organisms into these groups.
Only the aspects specifically relevant to recording biodiversity are considered here.
Hierarchical systems
A key step was to recognize that biological diversity can be ordered hierarchically:
- Individual organisms are grouped into species.
- Similar species are grouped into higher categories (e.g. genera, families, etc.).
The exact ranks and their definitions are treated in detail elsewhere. For the purpose of recording diversity, the hierarchy provides:
- A way to handle large numbers of species.
- A structure in which new discoveries can be placed.
- A scaffold for later evolutionary interpretation.
Fixed names instead of changing descriptions
To make recording diversity more precise and internationally usable, names had to be:
- Standardized
- Unique
- Stable as far as possible
This led, among other things, to:
- The use of Latin (and later partly Greek) words as a neutral, non-national language.
- The development of rules for naming, which are now codified in international codes (for animals, plants, fungi, bacteria, etc.).
Linnaean Naming and Its Role in Recording Diversity
Although the historical context belongs to another chapter, one specific innovation is central to this topic: binomial nomenclature.
Binomial nomenclature as a tool
Each species receives a two-part name:
- A generic name (genus; capitalized), e.g.
Homo - A specific epithet, e.g.
sapiens
Together, they form the species name: Homo sapiens.
For recording biodiversity, this system offers:
- Unambiguity: each species name refers to one taxon.
- Comparability: the same name is used worldwide.
- Structure: the genus grouping is already included in the name.
To avoid confusion, names are usually written in italics; the genus is capitalized, the specific epithet is not.
Type concept and name anchoring
When documenting species, it is important that the name is always linked to the same organism concept.
This is achieved through the type concept:
- For each species name, a concrete type specimen is designated.
- This is a preserved individual (or part of one) stored in a collection (e.g. herbarium, museum).
- The name is permanently tied to this specimen.
This does not mean that the entire species is identical to the type specimen; rather, the type serves as a reference point so that other scientists can check which organism the name actually applies to.
Institutions and Techniques for Recording Diversity
Collections: herbaria and museums
Recording diversity is not only about names and descriptions, but also about material evidence.
Two central types of institutions are:
- Herbaria: collections of dried, pressed plants and other preserved fungi and algae.
- Natural history museums: collections of preserved animals, fossils, and other biological materials.
Their roles in documenting biodiversity include:
- Providing reference material for species identification.
- Safely storing type specimens.
- Enabling reexamination of old records with new methods.
- Preserving evidence of species that may be rare or already extinct.
Labeling of specimens is crucial:
- Each specimen is given a unique collection number.
- Place, date, collector, and habitat are recorded.
- Later researchers can reconstruct the circumstances of the find.
Field methods: observation and sampling
To record biodiversity in nature, organisms must first be found and documented. Key practices include:
- Standardized surveys: e.g. transects, plots, or point counts to estimate which species occur and how frequently.
- Sampling methods suited to each group:
- Nets for insects or aquatic organisms
- Traps for small mammals or invertebrates
- Soil core samples for soil organisms
- Field notes:
- Exact locality (today often with GPS coordinates)
- Habitat type and environmental conditions
- Behavior, life stage, and associated species
These observations, together with collected specimens, form the raw data for later identification and classification.
Documentation: descriptions and illustrations
Proper recording of biodiversity requires concise and comparable descriptions:
- Morphological descriptions:
- Body shape, size, color, structures (e.g. leaves, wings, teeth)
- Use of standardized terminology to reduce ambiguity
- Illustrations and photos:
- Traditionally: detailed drawings showing diagnostic features.
- Today: high-resolution photographs and sometimes 3D models.
- Identification keys:
- Step-by-step tools that help determine species based on observable characteristics.
- Often structured as decision trees: “if character A, go to step 3; else go to step 4”.
Such tools allow other people, in other regions and times, to identify organisms consistently.
Quantifying Biodiversity
Recording diversity is not only about listing species, but also about measuring it.
Species richness and abundance
Two basic quantitative aspects:
- Species richness: how many species occur in a given area or community.
- Abundance: how many individuals of each species are present.
To estimate these, scientists:
- Conduct repeated surveys using standard methods.
- Record both the presence of species and counts or estimates of individuals.
- Use statistical methods to correct for undetected species.
These numbers are central for:
- Comparing regions (e.g. tropical vs. temperate forests).
- Detecting losses of biodiversity over time.
- Evaluating the success of conservation measures.
Sampling effort and completeness
Because not all organisms can be detected, recording must deal with incomplete data:
- More sampling usually reveals more species.
- At some point, additional effort finds mainly species already known from earlier samples.
To assess how complete a survey is, scientists may:
- Plot the species accumulation curve: the number of observed species vs. sampling effort.
- Use models to estimate total species richness in an area, including species not yet observed.
This is important for judging whether a region is well-documented or still underexplored.
Modern Approaches: From Morphology to Molecules
The recording of biodiversity has expanded from purely morphological approaches to include molecular methods.
Molecular markers and DNA barcoding
Molecular methods allow organisms to be distinguished based on DNA sequences.
A central concept is DNA barcoding:
- A short, standardized DNA segment (a “barcode”) is sequenced.
- Each species tends to have a characteristic barcode sequence or a small cluster of similar sequences.
- Unknown samples are identified by comparing their sequences to a reference database.
Typical barcode regions differ among organism groups but share the same purpose: fast, standardized identification.
For recording diversity, this brings several advantages:
- Identification of organisms that are difficult to distinguish by appearance alone (e.g. cryptic species).
- Work with incomplete or processed material (e.g. stomach content, environmental samples).
- Improved detection of early life stages (e.g. larvae, eggs) which often lack distinctive morphology.
Environmental DNA (eDNA)
Organisms leave traces of DNA in their environment (water, soil, air). eDNA methods:
- Collect environmental samples (e.g. water from a lake).
- Extract DNA from the sample.
- Amplify and sequence certain marker regions.
- Compare obtained sequences with reference databases.
This allows detection of species without directly observing or catching them, which is especially useful for:
- Rare, shy, or endangered species.
- Early detection of invasive species.
- Large-scale monitoring of ecosystem biodiversity.
Digital databases and global networks
Modern recording of biodiversity relies heavily on digital data management:
- Species names, descriptions, and distribution data are stored in large databases.
- Museum and herbarium specimens are being digitized (images, metadata).
- Genetic data are made available in sequence databases.
Examples of data types that are typically recorded:
- Taxonomic information (name, authority, synonyms)
- Occurrence records (where and when the species was found)
- Links to specimens, images, and DNA sequences
Global networks and platforms enable:
- Sharing of data across institutions and countries.
- Integration of citizen observations with professional records.
- Rapid updating of distribution maps and species checklists.
These digital infrastructures greatly increase the efficiency and reach of biodiversity recording.
Citizen Science and Public Participation
Recording biodiversity is a huge task; professional biologists alone cannot survey all regions and organism groups. Citizen science projects increasingly contribute to biodiversity data.
Key aspects:
- Trained laypeople observe and report species via apps or online platforms.
- Photos and location data are uploaded; experts and automatic tools help with identification.
- Large numbers of observations make it possible to:
- Track changes in species distributions.
- Detect phenological shifts (e.g. flowering time, bird migration).
- Recognize new or invasive species early.
For accurate recording, such projects often include:
- Simple identification guides.
- Quality control mechanisms (e.g. expert review, reputation systems).
- Standardized data formats so that observations can be integrated into scientific databases.
Challenges and Limits in Recording Biodiversity
Despite all methods and technologies, recording diversity faces significant challenges.
Incompleteness and bias
- Many species remain undescribed, especially in species-rich groups like insects, fungi, and microorganisms.
- Some regions (e.g. tropical forests, deep sea) are poorly explored.
- Studies often focus on larger, conspicuous organisms (birds, mammals, flowering plants), creating a bias in our knowledge.
This means that our current picture of global biodiversity is still only partial.
Taxonomic impediment
The taxonomic impediment describes the shortage of experts who can:
- Recognize and describe new species.
- Revise outdated classifications.
- Maintain and improve identification tools.
Training new taxonomists, securing funding for collections, and maintaining long-term projects are essential to overcome this barrier.
Dynamic nature of taxonomy
Because classification systems change as new data appear:
- Names can change (e.g. species moved to another genus, redefined, or merged).
- Species concepts may be broadened or split.
For recording biodiversity, this creates the need to:
- Track synonyms (different names for the same species).
- Maintain versioned taxonomic checklists.
- Ensure that older records can still be interpreted correctly in light of current taxonomy.
Importance of Recording Diversity for Other Areas of Biology
The systematic recording of biodiversity is not an end in itself. It forms a foundation for many other fields:
- Evolutionary biology: reconstructing relationships among species and tracing evolutionary changes.
- Ecology: understanding how different species interact and form communities.
- Conservation biology: identifying threatened species and areas with particularly high diversity.
- Applied fields: agriculture, medicine, and biotechnology often rely on knowing which species exist and where they occur.
Without accurate, standardized, and accessible records of biological diversity, these branches of biology would lack essential data for research and practical applications.