• Energy Research

Climate change leads to species range shifts and consequently to changes in diversity. For many systems, increases in diversity capacity have been forecast, with spare capacity to be taken up by a pool of weedy species moved around by humans. Few tests of this hypothesis have been undertaken, and in many temperate systems, climate change impacts may be confounded by simultaneous increases in human-related disturbance, which also promote weedy species. Areas to which weedy species are being introduced, but with little human disturbance, are therefore ideal for testing the idea. We make predictions about how such diversity capacity increases play out across elevational gradients in non-water-limited systems. Then, using modern and historical data on the elevational range of indigenous and naturalized alien vascular plant species from the relatively undisturbed sub-Antarctic Marion Island, we show that alien species have contributed significantly to filling available diversity capacity and that increases in energy availability rather than disturbance are the probable underlying cause.

AbstractGlobally, collapse of ecosystems—potentially irreversible change to ecosystem structure, composition and function—imperils biodiversity, human health and well‐being. We examine the current state and recent trajectories of 19 ecosystems, spanning 58° of latitude across 7.7 M km2, from Australia's coral reefs to terrestrial Antarctica. Pressures from global climate change and regional human impacts, occurring as chronic ‘presses’ and/or acute ‘pulses’, drive ecosystem collapse. Ecosystem responses to 5–17 pressures were categorised as four collapse profiles—abrupt, smooth, stepped and fluctuating. The manifestation of widespread ecosystem collapse is a stark warning of the necessity to take action. We present a three‐step assessment and management framework (3As Pathway Awareness, Anticipation and Action) to aid strategic and effective mitigation to alleviate further degradation to help secure our future.

ABSTRACTUnderstanding the processes that lead to species extinctions is vital for lessening pressures on biodiversity. While species diversity, presence and abundance are most commonly used to measure the effects of human pressures, demographic responses give a more proximal indication of how pressures affect population viability and contribute to extinction risk. We reviewed how demographic rates are affected by the major anthropogenic pressures, changed landscape condition caused by human land use, and climate change. We synthesized the results of 147 empirical studies to compare the relative effect size of climate and landscape condition on birth, death, immigration and emigration rates in plant and animal populations. While changed landscape condition is recognized as the major driver of species declines and losses worldwide, we found that, on average, climate variables had equally strong effects on demographic rates in plant and animal populations. This is significant given that the pressures of climate change will continue to intensify in coming decades. The effects of climate change on some populations may be underestimated because changes in climate conditions during critical windows of species life cycles may have disproportionate effects on demographic rates. The combined pressures of land‐use change and climate change may result in species declines and extinctions occurring faster than otherwise predicted, particularly if their effects are multiplicative.

Global Biodiversity Target Missed In 2002, the Convention on Biological Diversity (CBD) committed to a significant reduction in the rate of biodiversity loss by 2010. There has been widespread conjecture that this target has not been met. Butchart et al. (p. 1164 , published online 29 April) analyzed over 30 indicators developed within the CBD's framework. These indicators include the condition or state of biodiversity (e.g., species numbers, population sizes), the pressures on biodiversity (e.g., deforestation), and the responses to maintain biodiversity (e.g., protected areas) and were assessed between about 1970 and 2005. Taken together, the results confirm that we have indeed failed to meet the 2010 targets.

We welcome the correspondence from Watson and Segan [1] for highlighting the fact that there are both direct and indirect impacts of climate change on biodiversity conservation, and that the response of human communities will impact the likelihood of conservation success. Rapid growth in human populations and increasingly variable and severe weather events are increasing demand for natural resources and changing land-use and human settlement patterns. How this plays out across the planet depends on the effectiveness of a broad suite of economic, social, and conservation policies, along with the strength and stability of governance systems at multiple scales.

Species ranges are seldom at equilibrium with climate, because several interacting factors determine distribution, including demographic processes, dispersal, land use, disturbance (e.g., fire), and biotic interactions. Conservation strategies in a changing climate therefore cannot be based only on predicted climate-driven range shifts. Here, we explore conservation and management options in a framework for prioritizing landscapes based on two 'axes of concern': landscape conservation capacity attributes (percentage of protected area, connectivity, and condition of the matrix) and vulnerability to climate change (climate change velocity and topographic variation). Nine other conservation actions are also presented, from understanding and predicting to planning and managing for climate change. We emphasize the need for adaptation and resilience in populations, ecosystems, and the conservation environment itself.

AbstractUnder anthropogenic climate change, emerging diseases and pathogens are increasingly prevalent in high latitude and altitude regions that were previously protected by cold winter temperatures. Ongoing island‐wide dieback of a foundation species, the cushion plant Azorella macquariensis, on World Heritage listed Macquarie Island provides the first sub‐Antarctic example. To better understand the island‐wide progression of cushion dieback and its drivers, we established and quantified plant condition classes and measured microclimate across 62 sites. We then tested whether the drivers of cushion dieback were associated with (i) water stress: represented by vapour pressure deficit, wind exposure and gravel content, (ii) pathogen virulence: using freezing days and extreme humidity as empirically supported surrogates, or (iii) both. There was a strong north‐south progression in cushion condition, with dieback most active in the centre of the island and advanced in the north. Dieback was most extensive at sites with fewer freezing days and high humidity. Natural southern refugia were explained by the significantly colder temperatures, associated with a north‐south temperature gradient. It is expected that under current climate change trajectories, where Macquarie is likely to continue to become warmer and wetter, cushion dieback will remain pervasive, expanding most slowly in the south and potentially outpacing recovery. We emphasise the need for increased awareness to prevent the establishment of pathogens into and across the landscapes of newly susceptible high latitude and altitude regions. Areas of high conservation significance need to be prioritised for management, to prevent further landscape‐scale change under current climate trajectories.

In 2050, most areas of biodiversity significance will be heavily influenced by multiple drivers of environmental change. This includes overlap with the introduced ranges of many alien species that negatively impact biodiversity. With the decline in biodiversity and increase in all forms of global change, the need to envision the desired qualities of natural systems in the Anthropocene is growing, as is the need to actively maintain their natural values. Here, we draw on community ecology and invasion biology to (i) better understand trajectories of change in communities with a mix of native and alien populations, and (ii) to frame approaches to the stewardship of these mixed-species communities. We provide a set of premises and actions upon which a nature-positive future with biological invasions (NPF-BI) could be based, and a decision framework for dealing with uncertain species movements under climate change. A series of alternative management approaches become apparent when framed by scale-sensitive, spatially explicit, context relevant and risk-consequence considerations. Evidence of the properties of mixed-species communities together with predictive frameworks for the relative importance of the ecological processes at play provide actionable pathways to a NPF in which the reality of mixed-species communities are accommodated and managed. This article is part of the theme issue ‘Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere’.