Spatial and temporal changes in South African solar ultraviolet-B exposure: Implications for threatened taxa

• Spatial and temporal changes in South African solar UV-B (280-315 nm) exposure were modeled and mapped at 2.5 km2 resolution using ozone, relative humidity, cloud amount and elevation data. Computations indicated large natural gradients in UV-B exposure ranging from a 34.2% change over 14o of latitude to a 44.2% change over 16o of longitude. Modelling of future scenarios in annual UV-B exposure indicated small increases ranging from 2.5% in the year 2003 (best-case ozone depletion scenario) to 8.1% in the year 2051 (worst-case ozone-depletion scenario). Notable were substantial increases in intra-annual variability in UV-B radiation with ozone depletion. Exposure exhibits a 12% increase during late autumn (May) in the year 2003 and a 35% increase during this season in the year 2051. Taxonomic, life form and functional attributes were analyzed in 2146 threatened (rare, endangered, vulnerable) species representing 468 genera and 103 families, and their distributions compared with modeled spatial and temporal UV-B distribution patterns. The high fractions of evergreen and succulent life forms and geophytes, present among threatened taxa, indicate a high degree of physiological resilience to increased solar UV-B stress, though some life forms, e.g. trees, appear relatively less resistant. Conceivable reductions in per capita reproductive output and overall plant fitness were indicated in some plant functional types, e.g. herbaceous annuals, which may lead to altered patterns of species coexistence, floristic composition and diversity.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Publication and Content Type

art (subject category)

ref (subject category)