Showing papers by "Guy F. Midgley published in 2015"

Assessing species' vulnerability to climate change

Abstract: The effects of climate change on biodiversity are increasingly well documented, and many methods have been developed to assess species' vulnerability to climatic changes, both ongoing and projected in the coming decades. To minimize global biodiversity losses, conservationists need to identify those species that are likely to be most vulnerable to the impacts of climate change. In this Review, we summarize different currencies used for assessing species' climate change vulnerability. We describe three main approaches used to derive these currencies (correlative, mechanistic and trait-based), and their associated data requirements, spatial and temporal scales of application and modelling methods. We identify strengths and weaknesses of the approaches and highlight the sources of uncertainty inherent in each method that limit projection reliability. Finally, we provide guidance for conservation practitioners in selecting the most appropriate approach(es) for their planning needs and highlight priority areas for further assessments.

Future of African terrestrial biodiversity and ecosystems under anthropogenic climate change

Abstract: Projections of African ecological responses to climate change diverge widely. This Perspective unpicks some of the reasons for this uncertainty and reveals the importance of accounting for the influences of disturbancesand climate on vegetation. Projections of ecosystem and biodiversity change for Africa under climate change diverge widely. More than other continents, Africa has disturbance-driven ecosystems that diversified under low Neogene CO2 levels, in which flammable fire-dependent C4 grasses suppress trees, and mega-herbivore action alters vegetation significantly. An important consequence is metastability of vegetation state, with rapid vegetation switches occurring, some driven by anthropogenic CO2-stimulated release of trees from disturbance control. These have conflicting implications for biodiversity and carbon sequestration relevant for policymakers and land managers. Biodiversity and ecosystem change projections need to account for both disturbance control and direct climate control of vegetation structure and function.

Bud protection: a key trait for species sorting in a forest-savanna mosaic

Abstract: Summary Contrasting fire regimes maintain patch mosaics of savanna, thicket and forest biomes in many African subtropical landscapes. Species dominating each biome are thus expected to display distinct fire-related traits, commonly thought to be bark related. Recent Australian savanna research suggests that bud position, not bark protection alone, determines fire resilience via resprouting. We tested first how bud position influences resprouting ability in 17 tree species. We then compared the effect of both bark-related protection and bud position on the distribution of 63 tree species in 253 transects in all three biomes. Tree species with buds positioned deep under bark had a higher proportion of post-fire aboveground shoot resprouting. Species with low bud protection occurred in fire-prone biomes only if they could root-sucker. The effect of bud protection was supported by a good relationship between species bud protection and distribution across a gradient of fire frequency. Bud protection and high bark production are required to survive frequent fires in savanna. Forests are fire refugia hosting species with little or no bud protection and thin bark. Root-suckering species occur in the three biomes, suggesting that fire is not the only factor filtering this functional type.

Fire-mediated disruptive selection can explain the reseeder-resprouter dichotomy in Mediterranean-type vegetation.

Abstract: Crown fire is a key selective pressure in Med- iterranean-type plant communities. Adaptive responses to fire regimes involve trade-offs between investment for persistence (fire survival and resprouting) and reproduc- tion (fire mortality, fast growth to reproductive maturity, and reseeding) as investments that enhance adult survival lower growth and reproductive rates. Southern hemisphere Mediterranean-type ecosystems are dominated by species with either endogenous regeneration from adult resprout- ing or fire-triggered seedling recruitment. Specifically, on nutrient-poor soils, these are either resprouting or reseeding

An index for assessing effectiveness of plant structural defences against mammal browsing

Abstract: Plant structural defences against mammals play an important role in ecosystem functioning as they simultaneously mediate the fitness of both animals and plants. The efficiency of structural defences can be described by the amount of plant material an animal can remove in one bite. Quantifying bite size by direct observation is difficult requiring controlled access to both the plants of interest and the herbivores. A method called the bite size index (BSI) has been proposed using human bites to simulate the bite size of medium-sized mammalian herbivores. In this paper, we evaluated the utility of the BSI for assessing the efficacy of plant structural defences. We analysed the intra- and inter-specific variability of the BSI in an African savanna (Hluhluwe–iMfolozi, South Africa) rich in herbivores, its repeatability between recorders, how the results reflect known properties of plant structural defences and how well the index correlates with the bite size of goats and its efficacy for explaining species distribution on a fire–herbivory gradient. The BSI was readily applied to a large set (n = 55) of plant species and proved to be consistent among recorders (8 of the 9 recorders obtained similar estimates). Bite sizes of goats and human observers were strongly correlated for 14 plant species (R 2 = 0.70) with divergent leaf and branch types. An analysis of BSI for 55 plant species disclosed two main contributory factors: leaf dimensions and spinescence. The BSI was significantly related to plant species distribution on a fire–herbivore gradient in an African savanna.

BioMove - Improvement and Parameterization of a Hybrid Model fo the ASsessment of Climate Change impacts on the Vegetation of California

Abstract: There is substantial evidence that climate change is affecting ecosystems worldwide. California is no exception. With insights from historic climate change and subsequent species’ responses, scientists are developing refined tools to evaluate how species change may continue in the future and what impact this may have on biodiversity and conservation. Bioclimatic envelope modeling is one approach to modeling species distribution. However, it has many shortcomings by neglecting to account for individualistic species response or inter specific competition. Furthermore, bioclimatic envelope models do not account for species dispersal constraints or those imposed by disturbances such as land use change or fire. BioMove is a novel spatially explicit, dynamic species modeling approach developed to address these issues. It simulates a target species in a dynamic landscape, competing with a target species in competition with one or many PFTs. It combines various sub-models to integrate competition, dispersal and disturbance. It has important application potential for threatened species assessment, management coordination and decision support, invasive species modeling and other advanced climate change research.

Hydrological Niche of Restionaceae Species in Silvermine South Africa

Abstract: The Restionaceae species of the fynbos biome is part of the Cape floral kingdom, one of only six floristic kingdoms in the world. It is threatened by urbanization, agricultural expansion and groundwater extraction. Therefore, it is necessary to assess and monitor the Restionaceae species. South Africa is a semi-arid environment and hydrological factors are the main variables in the determination of species niches. This study investiagates the microclimate at Silvermine, and examines the contribution of hydrological variables to plant species distribution, thus creating a hydrological niche. This study generates its own unique microclimate hydrological datasets for modelling species niche. Additionally, this study assessed and modelled the effectiveness of the use of hydrological variables to determine species hydrological niche, at a microclimate level in a semi-arid environment. It also provided evidence regarding the importance of the study to conservation and future climate change impact analysis of plant species and species richness.