Original text by Jamie Slaven, revised and updated by Dr Steven Douglas in 2023
Berowra Valley National Park is valuable for recreation, Aboriginal and non-Aboriginal cultural heritage and for the large variety of indigenous plants and animals it contains. It is home to many plants (flora) and animals (fauna) listed as threatened species under the Biodiversity Conservation Act 2016 (NSW) and the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act, Commonwealth). A species of flora or fauna is defined as threatened if it is facing possible extinction in the short or medium term. Both NSW and Commonwealth laws classify such species into three categories. These are:
- Critically Endangered – considered to be facing an extremely high risk of extinction in the wild.
- Endangered – considered to be facing a very high risk of extinction in the wild.
- Vulnerable species – considered to be facing a high risk of extinction in the wild.
Both laws also list threatened ecological communities. The Biodiversity Conservation Act also lists Endangered Populations, all of which are currently legacy listings from the earlier Threatened Species Conservation Act (1995).
NSW and Commonwealth threatened biodiversity laws classify listings using the Common Assessment Method, which is adapted from the work of the International Union for the Conservation of Nature (IUCN). The IUCN’s system includes other classifications such as Data Deficient, Near Threatened, and Least Concern, as well as Extinct in the Wild, and Extinct. The EPBC Act also affords some protection to migratory species, which are primarily birds, and such listings may or may not also be threatened species.
Native species may become threatened by numerous factors such as deliberate or accidental destruction or degradation of habitat from a range of factors including land clearing; alteration of natural drainage systems; weed invasion; hybridisation (between native species and between native and non-native species); increased sedimentation and nutrient levels in stormwater run-off; removal of bush rock; altered fire regimes (frequency, intensity and seasonality); and predation or displacement by feral animals (e.g. foxes, cats and even honey bees).
Climate warming directly or indirectly threatens many species and communities and tends to cause additional stresses due to factors such as more frequent and severe droughts and/or floods, more extreme storms, and changes in the relationships between/within species such that they can break down. For example, changed climate can see an insect species mature and migrate earlier than normal, with it arriving well before the bird species that ordinarily controls its numbers has arrived. In the most extreme cases, this has already caused dramatic ecological change, with a forest ecosystem destroyed by over-abundant insects such that it is fast become a grassland. Climate warming can mean that habitats are modified such that species can no longer persist in their natural location and may have to move if they are able to and if suitable alternative habitat exists. Some animal species are likely to be able to adapt to climate warming by moving to different habitats. But most plants cannot move fast enough to shift to different environments.
In some cases, a native species may become threatened owing to its naturally small and/or isolated populations or because of very specific and restricted habitat requirements. Extinction is a natural process, and some species were in decline prior to non-Aboriginal colonisation. An example of this is Eucalyptus cryptica (formerly E. sp. Cattai) from the adjoining Hills Shire in the greater Cattai Creek catchment. This very rare small tree has likely lost habitat to urban and rural-residential land use but appears to have been rare and highly localised for a considerable time, possibly for genetic reasons and/or due to natural loss of habitat to erosion and long-term climate variation.
Current concerns about extinction relate to the vastly increased rate and extent of decline in many species, population, ecological communities, and ecosystems worldwide. The causes of this include destruction and fragmentation of habitat, pollution of various kinds, over-exploitation (hunting, fishing, harvesting, logging), predation or displacement by introduced pest plants or animals, and climate warming.
More native species and ecological communities may be listed as threatened if human impacts and other threats are not eliminated, or their impacts mitigated. Conversely, the status of some species may be reduced from Endangered to Vulnerable, and some may even be removed from the threatened species lists, should sufficient habitat be conserved and sustained, with other threats being eliminated or adequately reduced. There have been a very small number of species recently removed from the threatened lists due to discoveries that they are far more numerous and more secure than previously believed. Some such species have been shown to have ‘boom and bust’ ecologies in which they have naturally extreme fluctuations in population size ranging from very few (or even no) individuals to very many. After the 2019-20 wildfires in south-east Australia, some plant species that were previously very rare, experienced massive increase in the number of individuals in post-fire regrowth. These were assessed under the Common Assessment Method and were found to be no longer eligible for listing as threatened. Many are classified as ‘fire ephemerals’.
However, the trend is towards more species being listed as threatened and for the level of threat to be increased, for example from Vulnerable to Endangered. The lists of threatened species are not comprehensive and many plants and animals have not been assessed in recent years such that their status is not necessarily up to date. Many species of insects and fungi remain are yet to be described and published, and this is necessary to understand their conservation status. In many cases, we are very likely losing species before we have even identified or listed them.
All members of the public, as well as all levels of government, have a role to play in preventing native plants and animals from becoming extinct, and in promoting the recovery of threatened species. For lists of rare and threatened flora and fauna species in the Park, including their threat status, a description of selected species, and of their habitat, see the Appendices in this Guide.
Further reading
Cropper, S.C. 1993, Management of Endangered Plants,
CSIRO Publications, Melbourne
IUCN, 2000. IUCN Red List – Categories & Criteria v.3.1. https://portals.iucn.org/library/sites/library/files/documents/RL-2001-001.pdf