Large and robust landforms and geological features can withstand the impact of human activities with little effect, but many smaller scale and fragile types cannot. Examples of features threatened with total destruction by modern civilisation include estuaries, spits and tombolos, sand dunes, moraines, kettle lakes and tarns, fault traces, limestone caves, karst and stalactites, scoria cones, small volcanic craters, geysers, mud pools, fossil and mineral sites, and small rock exposures.
Erosion and weathering are slowly eating away at most features, but they are also responsible for maintaining systems such as sand dunes, beaches, deltas, moraines, badlands and rock exposures in a healthy state. Unless natural erosion has been modified by human actions and now threatens significant features, there seems little justification for interfering with nature's course.
The largest extractive industry in New Zealand is aggregate quarrying for building, road making, and railway lines. Its impact on river beds has greatly altered their natural erosional and constructional processes. Elsewhere, such as in Auckland city, whole volcanoes have been quarried away.
Sluicing, dredging, and mining for alluvial gold continue to have a major effect on fluvial and terrace features in Central Otago and Westland. Increased peat harvesting could threaten New Zealand's remaining undrained peat lands, such as those on the Hauraki lowlands.
Major works like dam construction, irrigation schemes, airports, refineries, and smelters also damage landforms and geological features. When such projects are being planned, important earth science features should be given as much consideration as flora and fauna values and economic benefits.
Reclamation of land from the sea constitutes another threat to valuable landforms. The provision of rubbish tips, sports grounds, industrial development, farmland and marinas has meant the destruction of thousands of hectares of estuaries, salt marsh, mangrove swamps, and natural coastline.
Geothermal fields in the central North Island are an important part of New Zealand's natural heritage. Exploitation of the underground steam and hot water resource for electricity generation and heating has had a major impact on surface features in a number of fields, especially Wairakei, Spa and Whakarewarewa.
As cities spread, the natural, irregular beauty of the countryside is levelled by large, earth-moving machines to accommodate housing, factories, motorways, water, gas, sewage, and electricity reticulation. In the process, the aesthetic values of a diverse and interesting landscape are destroyed and sterile urban environments created. It is time that local councils used the Resource Management Act as it was designed, to insist that all future subdivisions retain as much of the original landform character of an area as possible.
The construction of barriers to slow the rate of erosion on the coast or river banks has produced hundreds of kilometres of concrete and rock eyesores. They often obscure valuable rock exposures, destroy natural landforms and interfere with natural erosional and depositional systems. Stabilising fore dunes behind a beach, for example, may cut off the sand supply to an active dune system further inland.
Many valuable exposures of rock have been produced during roadmaking and quarrying. Well-intentioned efforts to rehabilitate these scars by spraying road cuts with grass seed, and backfilling quarries with rubbish or drowning them to form lakes, have destroyed many cuttings that were of scientific and educational importance.
Agricultural and horticultural practices have had a substantial impact on New Zealand's landforms and geological features. Forest clearance for farmland has accelerated erosion, modifying steep hillsides and natural watercourses and rapidly infilling swamps and lakes. Almost all of New Zealand's natural freshwater wetlands have been drained to provide more land for production. The natural soil profile has been disturbed over vast areas, making it extremely difficult to find unmodified examples of lowland soils for baseline studies.
Exotic forests now cover large areas of New Zealand. Planting processes disturb the natural soil profile and bulldozed forestry tracks scar many landscapes. More significantly, in many coastal areas, forest planting has threatened the very existence of representative examples of active dune systems.
Rare mineral specimens, fossils, and natural artifacts are vulnerable to over-collecting by scientists, rock hunters, and commercial operators. Some specimens should be deposited in museums where they can be studied in detail and interpreted in displays for the public's benefit, but in many instances they are best left in the rocks so that information about their settings can also be obtained.
Our spectacular landforms and geological features are attracting ever increasing numbers of tourists and recreational users. Unless properly managed, increased visitor numbers will do irreparable damage to some of our more fragile features. For example, with more people visiting the Waitomo caves, increased carbon dioxide levels in the passage ways was beginning to affect the delicate stalactite structures, until measures were taken to avoid this. Recreational and tourist facilities, such as ski fields and walking tracks, all need careful planning to minimise damage to smaller geological features and landforms.