📊 Surveys
Measuring biodiversity — the number and abundance of species in an area — is one of the foundational activities of ecology, conservation biology, and environmental monitoring. It sounds straightforward: go to a place, count the species. In practice, it is a complex scientific challenge that has generated an entire subdiscipline of statistical ecology. Species vary enormously in their detectability: a rhinoceros is easy to find, but a cryptic frog species or a rare soil beetle may require highly specialised survey methods to detect even when present. The relationship between the number of species detected and the number actually present is governed by detection probability — and accounting for imperfect detection is essential to producing estimates that are scientifically credible.
estimated species on Earth
described species to date
new species described annually
of terrestrial species undescribed
The most widely used methods for surveying vertebrate biodiversity are point counts and transects. In a point count, an observer stands at a fixed location for a fixed period — typically 5-10 minutes — and records all individuals of the target group (usually birds) detected by sight or sound within a defined radius. Repeated across many points in a systematic grid, point counts produce occupancy and abundance estimates for all detected species across a landscape. Transect surveys involve walking predetermined routes at a fixed pace and recording all target species encountered within a fixed distance on each side — providing distance data that allow rigorous statistical estimation of population density.
Environmental DNA (eDNA) methods — collecting water, soil, or air samples and sequencing the DNA of organisms that have left genetic traces — are revolutionising biodiversity assessment. A single water sample from a stream can reveal the presence of dozens of fish, amphibian, invertebrate, and mammal species through the genetic material shed into the water. eDNA surveys are particularly powerful for detecting rare, cryptic, or elusive species that are difficult to find by conventional methods — and for surveying aquatic environments where conventional methods (netting, electrofishing) cause disturbance and stress to animals.
The Field Museum's Rapid Biological and Social Inventories programme — a model replicated by many conservation organisations — conducts intensive 2-3 week surveys of proposed protected areas, deploying teams of 10-15 experts in plants, birds, mammals, fishes, herpetofauna, and insects simultaneously to document the biodiversity of areas that have never been scientifically surveyed. These rapid inventories have repeatedly revealed extraordinary biodiversity — including new species records, range extensions, and genuine species new to science — in areas threatened by immediate development or extraction. The logistical challenge is formidable: reaching remote forest sites typically requires days of river travel, helicopter drops, or overland trekking; equipment must survive humidity, flooding, and physical damage; and the concentrated effort of experts working 14-hour days must be coordinated to maximise taxonomic coverage in the limited time available. The scientific and conservation value of these inventories is substantial: documentation of biodiversity before disturbance provides baseline data for impact assessment, supports arguments for protection, and produces specimen collections and genetic samples that enable research for decades after the survey team has departed.
Standardised biodiversity assessment frameworks — including the Biodiversity Observation Network (GEO BON) essential biodiversity variables and the IUCN Red List assessment criteria — provide common currencies for comparing biodiversity surveys conducted by different teams using different methods, enabling the aggregation of local observations into global assessments that inform international conservation policy and reporting frameworks including the Convention on Biological Diversity's Kunming-Montreal Global Biodiversity Framework.
The Conservation International Rapid Assessment Program (RAP) pioneered the concept of multi-taxa rapid biodiversity surveys: expeditions of 2-4 weeks in which teams of specialists simultaneously assess plants, birds, mammals, herpetofauna, fish, and key invertebrate groups at sites with unknown or poorly known biodiversity. RAP surveys have documented spectacular biodiversity in areas previously unknown to science, including the discovery of over 1,300 species new to science across 70+ expeditions since 1990. The speed of RAP surveys requires methodological compromises — surveys are not exhaustive, and detectability of rare species in short surveys is limited — but the value of comprehensive multi-taxa assessment in a single expedition (which allows analysis of co-occurrence patterns and ecosystem-level interactions across taxa) often outweighs the loss of completeness compared to single-taxon studies. RAP surveys have been instrumental in establishing protected areas by providing scientific documentation of biodiversity value to government and international conservation bodies on timescales relevant to policy decision-making.
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Dr. Al-Rashid has led field expeditions across the Middle East, East Africa, and Southeast Asia for 13 years, studying threatened ecosystems, conducting biodiversity surveys, and developing community-based conservation programmes in remote regions.
The publication and open availability of rapid inventory datasets — including the specimen collections, photographic records, and GPS coordinates of all observations — multiplies the scientific value of each expedition beyond the immediate findings, providing reference materials for subsequent taxonomic revisions, historical baselines for monitoring future change, and training datasets for automated identification systems.