USGS Science⌕ Search
Home/Archive/USGS

USGS · 1008365

Estimating the magnitude of decline of the Florida torreya ( Torreya taxifolia Arn.)

Mark W. Schwartz·Sharon M. Hermann·Phillip J. van Mantgem
View original source ↗Export metadata ↓

Abstract

Torreya taxifolia is a coniferous tree that is endemic to the 35 km stretch of bluffs and ravines along the east side of the Apalachicola River in northern Florida and adjacent southern Georgia. This formerly locally abundant tree declined during the 1950s and 1960s as a result of disease and is currently on the US Endangered Species list. For sparsely distributed species it can often be difficult to determine both current and historic population sizes. Historical descriptions of the distribution (203 km 2 ) and relative abundance (14.2% of dominant ravine trees) of T. taxifolia are used along with current measures of forest structure to estimate the pre-decline population density (30 trees/ha) and size (∼0.3–0.65 million individuals). Survey information from five extant stands is used to estimate current population size (∼500–4000 individuals). The surveys were conducted in areas with known high tree densities such that a simple extrapolation to the entire distribution would produce a gross over-estimate of population size. We therefore use a variety of assumptions to produce a range of estimates for total population sizes. Regardless of the particular model, our estimates suggest that T. taxifolia has lost at least 98.5% of its total population size since the early 1900s. We discuss these results in relation to the potential difficulties likely of restoring sustainable populations of this species.

Explore related subjects

Biological ConservationArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Mark W. Schwartz, Sharon M. Hermann, Phillip J. van Mantgem. 2000. Estimating the magnitude of decline of the Florida torreya ( Torreya taxifolia Arn.). https://doi.org/10.1016/s0006-3207(00)00008-2

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Biome-scale spatial patterns of avian abundance reveal proactive conservation opportunities in North American grasslands

North American grassland birds have experienced steeper population declines than any other avian guild, yet conservation efforts remain largely reactive and fragmented. We used nearly four decades of North American Breeding Bird Survey data to identify biome-scale spatial patterns (clustering) of grassland bird abundance for the Great Plains. Our results reveal an ecological core in the north-central Plains where community-level abundance is either increasing by >100% or remains high and stable, providing a strategic roadmap for a “Defend the Core” conservation approach. This approach flips the script from reactive triage centered on isolated population fragments to a proactive strategy of maintaining large-scale ecosystem integrity. Conversely, we found that population losses are more spatially clustered than wins, reflecting the relentless, one-way movement of woody encroachment and agricultural conversion. This asymmetry supports prioritizing intact landscapes, as current restoration rates are often outpaced by the scale of habitat loss. Notably, we found that community-level spatial clustering is a more robust indicator of biome condition than trends of individual flagship species, suggesting that managing for ecosystem integrity provides a more effective multi-species umbrella. Given our results, there is an opportunity for operationalizing a Great Plains Conservation Design that is ecosystem-centric and rooted in the sustainability of the private-land cattle production that maintains these open spaces. By leveraging avian abundance as a biological sensor, managers and producers can deploy a shared vision that matches the spatial scale of the threats, moving from reactive triage to proactive defense of core working grasslands in North America.

Great Plains biome↗
USGS2026

Long lives, short futures: Freshwater turtle and tortoise imports to the United States highlight global trade and conservation challenges

Global trade of freshwater turtles and tortoises presents substantial conservation, biosecurity, and regulatory challenges, particularly for long-lived species that are already highly imperiled. While the United States has historically played a key role in supplying the international chelonian trade, investigations into its role as an importer remain limited. We used import data from the U.S. Fish and Wildlife Service Law Enforcement Management Information System (LEMIS) between 2000 and 2022 to evaluate the trade of freshwater turtles and tortoises. Over 2.5 million individuals were imported into the United States during this period, comprising 172 species that are likely imported for the pet trade, food, and traditional medicine markets. Reported annual imports for freshwater turtles increased until approximately 2013 and decreased thereafter, whereas reported annual imports for tortoises have remained relatively constant. Two species, Chinese softshell turtles ( Pelodiscus sinensis ) and Horsfield's tortoises ( Testudo horsfieldii ) represent 62.9% of all imports. Imported species were largely classified as Vulnerable, Endangered, or Critically Endangered by the IUCN Red List, yet the conservation status of a concerning number of species ( n = 45; 26.2%) has not been evaluated. Many imports appear to be sourced from wild populations (28.3% of freshwater turtles, 71.3% of tortoises); however, captive-sourced imports increased significantly over time across both groups. Import volumes raise concerns regarding the sustainability of freshwater turtle and tortoise trade, the potential for invasive species establishment, and disease spread. Our results highlight the need for updated IUCN assessments, verification of trade records, and strengthening of biosecurity screening at U.S. ports of entry.

Biological Conservation↗
USGS2026

Bird breeding success in restored grasslands compared to croplands and natural grasslands: A meta-analysis

Reproductive success is central to long-term population persistence, yet it is rarely assessed in ecosystem restoration. We performed a multilevel meta-analysis to assess whether bird breeding success increases from croplands to restored grasslands or from restored grasslands to natural grasslands. We quantified five comparisons of two breeding success variables between croplands and restored grasslands in three species, and 228 comparisons of nine variables between natural and restored grasslands in 22 species using 14 datasets from North America and Europe. For the few grassland birds that nest in croplands, clutch size was higher in restored fields than in croplands. Most importantly, breeding success did not differ between restored and natural grasslands in nine species and for all species combined. In 13 species, breeding success differed between restored and natural grasslands, and it was often higher in restored grasslands during early breeding stages, but higher in natural grasslands during later stages. Eight species did better in restored grasslands (Clay-colored Sparrow, Dickcissel, Eastern Meadowlark, Lesser Prairie-chicken, Mourning Dove, Red-winged Blackbird, Sprague's Pipit, Western Meadowlark), whereas four species did better in natural grasslands (Baird's Sparrow, Common Nighthawk, Lark Bunting, Savannah Sparrow). Our results suggest that bird breeding success can be as high in restored grasslands as in natural ones, and certainly higher than in croplands. While restored grasslands differ widely by geography, climate, method and management, our results offer hope for ecosystem restoration. However, the differences found also imply that species requirements should be considered in grassland ecosystem restoration and management.

Biological Conservation↗