Planning a Prosperous Sydney: The challenges of planning urban development in the new urban context

Since their post-war inception, Sydney's metropolitan plans have tended to be overtaken by the social, economic and environmental conditions they have had to confront. The depth and scope of Sydney's recent urban transformation threatens again to overtake metropolitan planning capacity creating, in the context of competitive globalisation, a potentially significant market disadvantage for the city, not to mention poor urban development outcomes. This paper reviews Sydney's post-war metropolitan planning strategies, examining the social and economic contexts and the policy paradigms in which they have been framed, in order to draw out the lessons to be learned from their successes and failures. We argue that future success in planning urban development will rely on richly informed and fine-grained understanding of the complex spatial outcomes of Sydney's ever-deeper global integration. Only such fine-grained understanding can empower metropolitan planning to be responsive to the evolving challenges of managing development in the contemporary urban context.     

Reefs at the edge: coral community structure around Rapa,southernmost French Polynesia

Rapa (27°36′ S, 144°20′ W) is a small (~40 km²) volcanic island isolated in the Southern Austral Archipelago, where direct anthropogenic stressors are extremely limited. Here, we present the results of the first quantitative survey of coral community structure across habitats and depths around the island. Despite its geographical isolation in the depauperate South Central Pacific, its small size and unfavourable environmental conditions (competition with macroalgae, low sea surface temperatures, reduced reef accretion), the diversity of scleractinian corals at Rapa is particularly high (112 species from 32 genera, including 37 species of Acropora) in comparison to other French Polynesian islands and subtropical Pacific locations. Our results indicate that the abundance (>100 colonies per 10 m² recorded at nine of the 17 sampling stations) and cover (>40% at four stations) of corals are relatively high for a marginal reef location. Strong spatial heterogeneity was found, with high variation in diversity, abundance, cover and community composition among stations. Variation in community composition was related to habitat types, with distinct assemblages among fringing reefs within bays, reef formations at bay entrances, and those on the submerged platform surrounding the island. On the platform, a depth gradient was detected, with generic richness, abundance and cover generally greater at deeper stations (18–20 m depth) compared with medium‐depth (10–12 m) and shallow (1–3 m) stations. A gradient was also recorded along bays, with increasing coral diversity and abundance from the bay heads to the bay entrances. The coral community at Rapa was characterized by the presence of several taxa not found in other French Polynesian archipelagos and the rarity of others that are common and abundant in the Society and the Tuamotu islands. Another distinctive feature of reef communities at Rapa is the high cover and dominance of macroalgae, particularly in the shallower parts of the surrounding platform, which probably explains the lower densities of coral colonies recorded there. These characteristics of the diversity and biogeographical composition of coral assemblages at Rapa provide considerable ecological grounds for its conservation.     

The geochemistry of Dinantian volcanism in south Kintyre and the evidence for provincialism in the southern Scottish mantle

Scottish Dinantian transitional to mildly alkaline volcanism is represented by abundant outcrops in the Midland Valley, Southern Uplands and Highlands provinces. Dinantian volcanic rocks from Kintyre in the Scottish Highlands range in composition from basalt through basaltic hawaiite, hawaiite, mugearite and benmoreite to trachyte, the compositions of the evolved types being largely due to differentiation from the basaltic parents.Recent geochemical investigations of Scottish Caledonian granitoids, Siluro-Devonian Old Red Sandstone (ORS) lavas and xenolith suites from numerous vents and dykes of Permo-Carboniferous to Tertiary age have revealed that the Scottish crust and upper mantle both increase in age and are increasingly enriched in incompatible elements towards the north and northwest. The upper mantle and lower crust below the Highlands province are therefore largely considered to be more enriched and in parts older than those below the Midland Valley and Southern Uplands. Dinantian alkali basalts from these latter two provinces have Nd values predominantly in the range +3 to +6, initial ⁸⁷Sr/⁸⁶Sr values of 0.7029–0.7041 and ²⁰⁷Pb/ ²⁰⁴Pb values of 15.48–15.60. However, similar basalts from Kintyre and Arran in the Highlands have lower Nd (+0.1 to +3.4) and ²⁰⁷Pb/²⁰⁴Pb (for given ²⁰⁶Pb/²⁰⁴Pb ratios; 15.49–15.51) and slightly higher ⁸⁷Sr/⁸⁶Sr (0.7033–0.7046). This regional variation correlates well with the differences seen between Midland Valley and Highland magmas in the ORS calc-alkaline suite (Thirlwall 1986) and it is suggested that both the ORS and Dinantian basic rocks are derived from similar types of mantle, although no lithospheric slab component is present in the later Dinantian suites. Isotopically-distinct portions of mantle therefore appear to have been present below the Highland and Midland Valley-Southern Upland provinces from at least Caledonian to Carboniferous times. The combined incompatible element and Sr-Nd-Pd isotopic evidence from Kintyre and Arran basaltic rocks does not allow unequivocal distinction between a lithospheric mantle and a sublithospheric mantle source. The observed correlation between isotopic composition of Dinantian basalts and the chemical composition of the lithosphere, together with the apparent involvement of long-term separated source reservoirs suggests that Kintyre and Arran lavas were derived largely from a lithospheric mantle source. On the other hand, the isotopic enrichment of Kintyre basaltic rocks is not extreme; trace element and isotopic compositions are still comparable to modem OIB. Sublithospheric mantle could therefore also be a viable source for Kintyre and Arran Dinantian volcanism.     

The breakdown of potassium feldspar at high water pressures

The equilibrium position of the reaction between sanidine and water to form “sanidine hydrate” has been determined by reversal experiments on well characterised synthetic starting materials in a piston cylinder apparatus. The reaction was found to lie between four reversed brackets of 2.35 and 2.50 GPa at 450 °C, 2.40 and 2.59 GPa at 550 °C, 2.67 and 2.74 GPa at 650 °C, and 2.70 and 2.72 GPa at 680 °C. Infrared spectroscopy showed that the dominant water species in sanidine hydrate was structural H₂O. The minimum quantity of this structural H₂O, measured by thermogravimetric analysis, varied between 4.42 and 5.85 wt% over the pressure range of 2.7 to 3.2 GPa and the temperature range of 450 to 680 °C. Systematic variation in water content with pressure and temperature was not clearly established. The maximum value was below 6.07 wt%, the equivalent of 1 molecule of H₂O per formula unit. The water could be removed entirely by heating at atmospheric pressure to produce a metastable, anhydrous, hexagonal KAlSi₃O₈ phase (“hexasanidine”) implying that the structural H₂O content of sanidine hydrate can vary. The unit cell parameters for sanidine hydrate, measured by powder X-ray diffraction, were a = 0.53366 (±0.00022) nm and c = 0.77141 (±0.00052) nm, and those for hexasanidine were a = 0.52893 (±0.00016) nm and c = 0.78185 (±0.00036) nm. The behaviour and properties of sanidine hydrate appear to be analogous to those of the hydrate phase cymrite in the equivalent barium system. The occurrence of sanidine hydrate in the Earth would be limited to high pressure but very low temperature conditions and hence it could be a potential reservoir for water in cold subduction zones. However, sanidine hydrate would probably be constrained to granitic rock compositions at these pressures and temperatures. Received: 6 May 1997 / Accepted: 2 October 1997     

Burrowing and burying by the crab Macrophthalmus hirtipes

Macrophthalmus hirtipes (Jacquinot, 1853) excavates burrows under water in soft, muddy sand that remains waterlogged at low tide. The crabs are immersed for at least 4 h in every tide. The burrows are usually single, blind‐ending, slightly curved passages; their openings do not appear to be deliberately closed by the crabs. Excavation is effected by using one set of walking legs as a scoop while the other set provides sideways traction.

Burrow openings are readily obscured by water movement, so that apparent burrow density does not give a true indication of the number of crabs in an area, but only indicates how many have been active recently; the true density may be found by sieving.

The burrowing activity of M. hirtipes is compared with that of other ocypodid crabs, and the functions of burrows are discussed. A distinction is made between excavating a burrow and rapid burying, because the two behaviours are very different, and must involve different adaptations and selection pressures.