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Sources of biodiversity data

Of an estimated 80,000 or more native animals, fungi and plants in New Zealand, only about 30,000 have been formally described, named and classified by taxonomists (see Table 9.1). Most of the undescribed species are fungi and invertebrate animals, particularly nematode worms and insects. Several hundred plants are also undescribed. On the other hand, it is well known globally that about 20 percent of current species names are synonyms (that is, different names for the same species). These uncertainties should be borne in mind when consulting Table 9.1 which provides a very approximate estimate of the number of species known and suspected in each major living group.

Apart from the uncertainty surrounding the number of species and their identities, considerable uncertainty also surrounds the population status and viability of many known species. Although much data exists on the ecology and behaviour of our more visible and endangered plants and animals, monitoring and research tends to be sporadic and poorly coordinated for most species and ecosystems.

Research on the taxonomy and ecology of indigenous species is carried out by many organisations, particularly universities, the major museums, and several research institutes, notably Landcare Research and the National Institute of Water and Atmospheric Research (NIWA). Most biodiversity research is funded through the Government's Public Good Science Fund and the Department of Conservation. The Department's declining budget, from its inception in 1987 until 1995, has been identified as one of the factors limiting biodiversity research (Halloy, 1995). The small increase in the latest financial year targeted pest control and species recovery programmes rather than research. Recently, however, the public funding for taxonomic work has had a million-dollar increase.

Table 9.1: Indigenous and introduced species in New Zealand (excluding extinct species)
Major taxonomic groups Estimated number of indigenous species2 Number that have been described Percentage of described species that are endemic Described species known to be threatened3 Number of introduced species in the wild
Single-Celled Bacteria4 ? c 200-300 ? ? ?
Protozoans4 c 7,500 c 2,600 5%? ? c 100
  • Land and freshwater
3,200 c 700 5%? ? ?
  • Marine species
3,300 c 1,650 5%? ? ?
  • Parasitic species
1,000 c 250 5%? ? c 100
Algae4(see also lichen fungi below) c 4,000 c 3,700 ? ? ?
Micro-algae (plankton, periphytons) c 3,000 c 2,800 ? ? ?
  • freshwater
c 2,200 c 2,100 ? ? at least 6
  • marine
c 800 c 700 ? ? ?
Multi-Celled Species Macro-algae (seaweeds) c 1,000 c 900 43% none at least 3
Plants4 c 3,400 c 3,080 65-70% c 300 c 1,900
Mosses, liverworts, hornworts c 1,100 c 1,060 20-40% c 85 13
Vascular plants c 2,300 c 2,022 81% c 200 1,896
  • Ferns and allies
c 200 189 46% at least 15 26
  • Gymnosperms (conifers)
20 20 100% none 28
  • Angiosperms
c 2,100 1,813 84% c 180 1,842
Fungi4 c 22,000 c 5,800 ? c 200 c 2,000
  • Lichens (fungi which harbour algae)
c 1,800 c 1,300 ? ? ?
Other (mushrooms, rusts, yeast, blight, etc.) c 20,000 c 4,500 ? ? ?
Invertebrate Animals4 c 52,000 c 20,500 ? c 200 c 2,200
Arthropods c 27,300 c 14,400 ? ? c 1,200
Insects (beetles, bees, flies etc.) c 20,000 c 10,000 90% c 175 c 1,100
Arachnids (spiders, mites etc.) c 4,600 c 2,600 90% 510 c 60
Pycnogonids (sea spiders) c 120 53 ? ? ?
Crustacea (crabs, copepods, slaters etc) c 2,000 1,517 ? 5 ?
Myriapods (millipedes, centipedes etc) c 600 c 200 ? ? ?
Molluscs c 4,800 c 2,500 ? ? c 40
Land and freshwater snails and slugs c 1,300 c 500 100% 15 c 33
Marine species (snails, shellfish, squid etc) c 3,500 c 2,000 ? ? at least 6
Worms (many phyla) c 17,500 c 1,500 ? ? c 980
Nematodes (roundworms etc.) c 11,400 414 43% ? c 600
Annelids
  • earthworms
220 178 100% at least 3 c 25
  • other (marine polychaetes etc.)
c 4,200 c 430 30-35% at least 1 c 230
Platyhelminths (flatworms, cestodes etc.) 430 80 56% at least 3 c 75
Other worms (spiny-heads, tunicates etc.) c 1,200 c 400 ? ? c 50
All Other Invertebrates5 c 2,600 c 2,100 ? ? ?
Vertebrate Animals4 c 1,500 c 1,250 21% c100 90
Fish
  • sea-dwelling marine species
c 1,100 c 870 5% 2 ?
  • rockpool marine species
c 100 94 62% 9 ?
  • freshwater species
c 35 28 90% 10 20
Amphibians (frogs) 4 4 100% 4 3
Reptiles 61 61 100% 25 1
Birds
  • land and freshwater
88 88 57% 37 34
  • seabirds
61 61 30% 18 0
Mammals
  • land-based
2 2 100% 2 34
  • marine mammals
416 41 5% (2 spp.) 4 0
TOTAL (multi-celled species only)4 c 80,000 c 30,000 ? c 800 c 6,000

1 No inventory of biodiversity has been attempted since the National Museum's 1980 symposium on the NZ biota (Brownsey and Baker, 1983). This table draws on that work and on the opinions of several current taxonomists, but is far from definitive.

2 Total species estimates are highly uncertain, except for plants and vertebrate animals.

3 Full species only. If sub-species were included, the total number of known threatened taxa would be about 1,000.

4 Given the imprecision of many of these figures, all totals and sub-totals have been rounded to avoid spurious accuracy.

5 Includes 350 known sponges, 400 cnidarians, 400 echinoderms, 900 bryozoans, and about 50 species from minor phyla.

6 Includes 34 cetaceans and 7 pinnipeds, many of which are visitors and seasonal migrants.

Reviews of the biological sciences by the Ministry of Research, Science and Technology (1992, 1993) found that ecological research in New Zealand is thinly spread and uncoordinated while taxonomic research is in marked decline. The number of scientists doing taxonomic work has fallen radically since 1980, to the point where retired scientists have been prevailed upon by Landcare Research to identify species of freshwater algae, mushrooms and grasses, and the National Museum of New Zealand employs retired staff and Ph.D. students on a part-time basis to undertake taxonomic work on its vast collections of unidentified species.

Despite the lack of coordinated research and the relative scarcity of information on many species, a wide range of ad hoc information and case studies exist relating to particular species or phyla. In some cases, disparate information has been drawn together in key publications (e.g. Williams and Given, 1981; Brownsey and Baker, 1983). Biodiversity databases are located in a variety of institutions. Landcare Research, for example, maintains native plant, fungus, plant bacteria and arthropod databases. NIWA maintains a freshwater fish database which is updated twice a year, as well as commercial marine fish stock databases. Other databases on species identification, distribution or conservation status are held by universities, museums, professional associations (e.g. the Ornithological and Botanical Societies) and the Department of Conservation.

Key information sources used in the preparation of this report have included species and stock assessments by the the Ministry of Fisheries (Annala 1995a, 1995b), Department of Conservation (1992b, 1994b, 1994e), the New Zealand Botanical Society (E.K. Cameron et al., 1993, 1995) and Landcare Research (Buchanan and Beever, 1995).

The Ministry of Fisheries' assessments cover about 40 fish species, representing about 2 percent of our fish biodiversity, and about half a dozen marine invertebrates. The assessments are undertaken by 13 working groups convened by the National Institute of Water and Atmospheric Research (NIWA) under contract to the Ministry of Fisheries. The working groups are led by marine scientists and also include representatives of the fishing industry, Māori tribes, recreational fishing groups and environmental groups. The panels work primarily from catch data and trawl survey data to assess each stock's reproduction rate and distribution.

The Department of Conservation's species assessments cover a broader range of species and are based on far less information. The Department has published a draft status list for marine organisms (Department of Conservation, 1994e) and a periodically updated list of threatened land and freshwater organisms, ranked according to their conservation priority (Department of Conservation, 1992b, 1994b). The Department lists as 'threatened' any species or sub-species which falls into one of the following internationally defined categories: endangered; vulnerable; rare; indeterminate; and insufficiently known.

The conservation priority of each species is reviewed by panels of experts which include Department staff and scientists from Crown Research Institutes, universities, private consultancies and environmental organisations (Department of Conservation, 1992b, 1994b). Threatened species are placed into ranked categories (A, B and C) or unranked ones (I, O and X). Category I, the single largest category, contains 324 taxa which are presumed threatened, but for which there is insufficient information to rank their priority.

The need to prioritise threatened species is largely an economic one because funds are limited. As a result, priorities in biodiversity research are often hotly debated, with arguments about which species should be targeted, whether to focus on genetic investigations or population studies, or whether to shift away entirely from species-centered research toward more ecological research.

In a recent review, which concluded that biodiversity research is under-funded and poorly coordinated, Halloy (1995) opened the priorities debate wider. He suggested that, while the main priority in New Zealand's biodiversity research should continue to be the preservation of native endemic species, there is also scope for including some introduced species. With our low population density and high social and economic stability, New Zealand could consider becoming an international 'ark' for rare breeds and endangered species which are no longer safe in their homelands. Exotic species have an ambiguous status in New Zealand. Farmed species are the backbone of our economy but feral species impose heavy pest control costs. In either case, they tend to be hostile to indigenous ecosystems and biodiversity. This Jekyll and Hyde quality means research on exotic species is needed both to manage their economic use and to control their ecological effects (see Box 9.3).

Considerable research effort is also now going into the economic uses of native species. Most of this research is privately funded and, apart from fish stock assessments, its focus is not on population or ecological status, but on chemical properties which may be of use in the manufacture of pharmaceuticals and industrial chemicals (bioprospecting). The biochemical research has focused mostly on plants and algae. Although this research is enabling more unknown species to be identified, and also provides a rationale for preserving potentially valuable species, it makes no direct contribution to assessing their status or the pressures they face. Indeed, for some species, it may increase the pressure by creating a hitherto non-existent demand for them.

Present information on New Zealand's biodiversity is scattered. Most of our indigenous fungi and invertebrate animals have not been identified, and the status of most species is not monitored. Information is best on vertebrates and vascular plants. Fungi, mosses, invertebrates, protozoans, algae and bacteria are less well known. Privately funded research focuses more on the potential uses of biodiversity than on its conservation status and ecology.

Standard methods of classifying and measuring the status of our biodiversity have not yet been devised, but considerable research effort is going into this at regional and national levels, including work by the Department of Conservation and the research institutes on ecosystem monitoring, and by the Ministry for the Environment on developing a core set of national biodiversity indicators (Ministry for the Environment, 1996a, 1996b).

Box 9.3: Sustainably managing our exotic biodiversity

Apart from marine fish and invertebrates, nearly all of New Zealand's economically important species, including pests and weeds, are exotic (i.e. introduced from other countries). This exotic biodiversity consists of 33 mammals, 33 birds, 1 lizard, 3 frogs, 20 freshwater fish, perhaps 1,000 invertebrates, about 100 parasitic protozoans, and perhaps 6,000 plants (nearly 2,000 of which are now established in the wild). Of these, about 25 animals and 120 plants are commercially farmed or cultivated, though the vast bulk of production comes from just 5 animals (chickens, sheep, cattle, deer, pigs) and 40 plants (pasture grasses, pine and Douglas fir trees, barley and other grain crops, peas, potatoes and other vegetables, grapes, kiwifruit, apples and other fruit).

The commercially important species are each divided into breeds, and these in turn are divided into strains, varieties and lines. Although some lines have been selectively bred here and are physically unique, none is genetically novel. This is because selective breeding does not create new genes, it simply reshuffles and sifts existing ones. Reshuffling is achieved by hybridising among breeds and varieties. Sifting is carried out over several generations by selective inbreeding among the hybrids. The result is actually a reduction in genetic diversity as unwanted genes are selected out of the gene pool until, eventually, all members share identical genes for a desired trait (e.g. placid temperament, fast growth rate, drought tolerance, high yield etc.). The genetic diversity of crop and livestock species is therefore only partly represented in any one strain or variety. This makes each one important, including wild variants and ancestral stocks, because each holds a unique subset of its species' total gene pool, though, in the case of recently developed strains and varieties (such as those in New Zealand) the genetic loss would be minor as they differ little from their parent stocks.

Maintaining diverse breeds and varieties is important for commercial as well as genetic reasons. It could take years, or even decades, of special breeding programmes to recreate a lost variety from its parent stock or related breeds. The only way to ensure that they are not lost, is to maintain their genes, either in living populations, or in collections of seeds, tissues, semen and embryos. However, this is costly so only those breeds and varieties considered to be of high priority are conserved in this way. New Zealand's Plant Variety Rights Act 1987 creates an economic incentive to develop new strains and varieties by protecting the breeder's propagation rights. However, there is no equivalent measure for encouraging the conservation and storage of existing stocks.

The loss of crop diversity is a global problem, and the need to conserve and sustainably use agricultural biodiversity is recognised in the 1992 United Nations Convention on Biological Diversity. The decline has been gathering pace for the past century as genetically uniform, high yield varieties have replaced traditional local varieties (Hawksworth et al.,1995). High yielding varieties are more profitable, in part because they have been bred for disease and pest resistence. Nevertheless, the low genetic variation of some widely distributed varieties makes them vulnerable to unfamiliar diseases and pests. Examples of such crop failures include: the potato famine of Ireland last century; a grape blight that wiped out valuable vines in France and the United States; a virulent disease that has wiped out banana crops in Central America; and a mould that infested hybrid maize in Zambia. To deal with such threats, the continuous development of new varieties is essential and this requires ready access to a broad range of existing genetic material (e.g. traditional varieties and wild relatives) from which to breed. Some overseas crops have been rescued from epidemics by using genes from older, forgotten varieties, or from wild relatives, to develop new varieties. The rescued crops include: potatoes; rice; sweet potatoes; wheat; maize; sugar beet; and rubber (Holden et al., 1993).

Despite their differences in outward appearance (phenotype), the plant and animal breeds of a given species are similar at the genetic level. This is because even the oldest breeds have had little time to evolve any new genetic diversity. It takes a million or more years for random mutations and natural selection to produce genetically distinct species. Plant and animal domestication is just several thousand years old. Like civilisation itself, it is a recent, late development in human history.

Our oldest domesticated species is the dog, bred in Eurasia from wild canids (wolves and jackals) more than 12,000 years ago (Davis and Valla, 1978; Olsen, 1985). The oldest skeletal remains of a domestic dog were found in Israel, but a skeleton from Idaho in the United States is nearly as old, at more than 10,000 years. Wolf, jackal and dog genes remain very similar, and all of today's 500 dog breeds are genetically close. Yet, by selecting and winnowing just a few key genes over many generations, dog breeders have managed to produce a wide variety of physical and behaviourial differences - and also a raft of inherited disorders from inbreeding (Bonner, 1994).

In contrast, cats, which were domesticated in Egypt only about 4,000 years ago, show much less diversity. Most of our other domesticated animals and crops were acquired between the taming of these two species. New Zealand's agricultural biodiversity, therefore, has its evolutionary roots in the early civilisations of Europe, Asia and the Americas.

The labour-intensive business of crop farming originated in the Middle East about 10,000 years ago and was followed shortly after by animal herding. The first crops of wheat (Triticum spp), barley (Hordeumi spp ), oats (Avena spp) and rye (Secale spp) were bred from grain-bearing wild grasses (cereals), and peas were domesticated from pod-bearing wild legumes (Zohary and Hopf, 1993; Solbrig and Solbrig, 1994). This revolutionary development seems to have been driven by hard times as the world's first urban populations, at Jericho, Tel Aswad and other East Mediterranean sites ran out of wild food sources (Wright, 1994; Bunney, 1994).

It took several thousand years for Middle Eastern farmers to spread out from the area that is now Turkey and around the Mediterranean into Europe (Lewin, 1996a). During this time, wild cereals were independently domesticated in several other parts of the world. Rice (Oryza spp) seems to have been first domesticated in China's Yangtze Valley (Normile, 1996) and by 7,000 years ago was being grown in southern Asia. By then, millet (Setaria spp)and sorghum (Sorghum spp) were being grown in Africa and maize (Zea spp) may have been domesticated in South America, though it did not become widespread there until much later (Hawksworth et al.,1995; Mestel, 1993). When agriculture reached Europe 7,000 years ago, it also inspired the cultivation of flax for linen. Fruits and nuts (e.g. figs, dates, grapes) were domesticated in the Middle East about 4,000 years ago. By the time of the Roman Empire (1,6002,000 years ago), almost all of today's crops and domestic animals were being farmed (Diamond, 1994; Solbrig and Solbrig, 1994). Developments since then have largely focused on creating new breeds and varieties.

The first domesticated food animals also arose in the Middle East: the pig more than 9,000 years ago; sheep and goats a little later; and western cattle (Bos taurus) about 7-8,000 years ago (Clutton-Brock, 1987; Diamond, 1995b; Hyams, 1972; Loftus et al., 1994). The wild ancestors of all these species were probably attracted to crops and scrap heaps on the outskirts of the world's first towns. Cattle became both a food source and a form of slave labour for transport and ploughing. They were later joined as beasts of burden by the tamed African wild ass, or donkey. Horses came later, from the north. They were tamed in the Russian steppe grasslands, about 6,000 years ago, by the warrior Kurgans who then rampaged east and west, taking both the horses and their Indo-European culture and languages into Europe, Iran, northern India, the Hittite Empire of the Middle East and the Tocharian settlements along the mountain trade route into western China (Anthonyet al., 1991; Diamond, 1991). By 4,000 years ago, Indian civilisation had tamed zebu cattle (Bos indicus), several species of buffalo, and the wild red jungle fowl, which, as the humble chicken, is now the most abundant livestock animal on Earth, numbering more than 10 billion - against 1.3 billion cattle, 1.2 billion sheep, and 850 million pigs.

Today, the world's eight main livestock mammals (western and zebu cattle, sheep, goats, pigs, buffalo, horses and asses) comprise about 3,000 breeds, of which nearly 400 (14 percent) are considered to be at risk of dying out (Hawksworth et al., 1995). Only nine of the many chicken breeds are widespread; most of the minor breeds and varieties are declining and some have disappeared. The UN Food and Agricultural Organization has recently estimated that the world has about 30,000 species of edible plant species, of which 7,000 have been grown for food (FAO, 1996). However, only 150 species are commercially important, and 90 percent of the world's food crops come from just 100 of these. Even this diversity is reduced when it is realised that more than half our plant energy intake comes from species and varieties of just three grasses: wheat, rice and maize. Despite their low species diversity, many crops have yielded hundreds or even thousands of varieties in several thousand years of cultivation. For example, the main species of rice (Oryza sativa) has 100,000 distinct varieties. In all, an estimated 1 million varieties of plants are now threatened (Edwards, 1996).

An inventory of 'at risk' exotic biodiversity has yet to be compiled for New Zealand. Our domestic animals include: cattle (two species), sheep, pigs, goats, deer (several species), horses, donkeys, dogs, cats, poultry (chickens, ducks, geese, turkeys), and more recent imports such as alpaca, llama, water buffalo, emu and ostrich. We have about 40 cattle breeds and 30 sheep breeds with several additional derived sheep breeds, such as Coopworth (bred from Romney and Border Leicester hybrids) and Perendale (bred from Romney and Cheviot hybrids). Pedigree lists of pure breeds are often maintained by a Breed Society. The New Zealand Pastoral Agriculture Research Institute (AgResearch) holds most of the semen for beef cattle and sheep. Dairy cattle semen is held by artificial insemination organisations. The Livestock Improvement Corporation has the largest store, though some semen is stored under contract to private breeders.

Most of New Zealand's factory farmed chickens are hybrid varieties, specially bred by international corporations. New Zealand franchise holders are regularly supplied with the latest breeding stock so no effort is made to retain superseded varieties or develop new ones. The local poultry industry is supplied by two companies, Hi-Line International (Iowa, U.S.A.) and I.S.A. (France), whose hybrid varieties, with names like Hi-Line W77, combine the genes of several standard breeds (e.g. Mediterranean Leghorn, New Hampshire, Rhode Island Red). These state-of-the-art birds are selectively bred to quickly lay eggs (up to 320 per year) or put on meat (reaching 1.8 kg in 5 weeksfive times faster than a 'normal' chicken). At present, the New Zealand industry processes about 62 million meat chickens and 2.4 million egg-layers per year.

The four main commercial pig breeds are Large white, Land race, Duroc and Hampshire. The New Zealand herds differ little from those overseas. About half come from stock supplied by two organisations, the Pig Improvement Company and the National Pig Breeding Company. These maintain small nucleus herds whose gene lines are constantly improved through regularly imported semen and selective breeding. Semen is not stored. With pigs, chickens and other livestock, small populations of pure breed and non-commercial varieties are kept by private enthusiasts, many of whom are affiliated to the Rare Breeds Association. Other exotic species that are economically important are introduced earthworms, honey bees and biocontrol insects.

Forage plants (i.e. grasses, clover and other plants for animals to graze) are New Zealand's most economically important plant genetic resource, both for pastures and lawns. Yet New Zealand has genetic samples of fewer than 7 percent of the world's grass species. The national forage collection is held as seeds at AgResearch's Margot Forde Centre in Palmerston North, which is an Australasian regional centre for temperate forage species. The Centre is recognised as having a collection of national importance by the Foundation for Science, Research, and Technology (FRST) and funding is relatively secure. Private breeding firms have their own working collections of forage plants, but do not maintain unprofitable breeding lines.

The main collections of field and vegetable crops are held by the New Zealand Institute for Crop and Food Research Ltd (Crop and Food), though several minor collections (e.g. hops) are held by the Horticulture and Food Research Institute of New Zealand Ltd (HortResearch) at the Riwaka Research Centre, Motueka. The New Zealand hops collection is free of many pests and diseases found in other countries. These collections receive government funding on the basis that they are 'Collections of Significant National Importance'. Such funding is confined to economically important varieties of wheat, barley, oats, maize, peas, onions, potato, kumara and some vegetables. HortResearch also maintains the only comprehensive fruit gene collections in New Zealand. Some of these, such as the apple and kiwifruit collections, are among the most important in the world. The kiwifruit collection is the best outside the fruit's homeland, China. The Asian peaches and nectarines collection is unique outside Asia, and the apricot collection is rich in genetically diverse material with cultivars from North America, southern and northern Europe and North Africa.

Collections of nut crops are held only by private individuals so their conservation is not underwritten by any public agency at present. The Novel Crops Programme run by Crop and Food includes a collection of native and exotic plants and animals whose desirable attributes include extracts, medicinal uses, aromatic properties and spices (Halloy 1995). HortResearch holds a collection of plants and seeds at Aokautere, near Palmerston North, selected for soil conservation and shelterbelt purposes. The collection is used to breed new plants for farmers. The Institute's collection of willow (Salixspp) and poplar (Populus spp) varieties is of world importance. The Forestry Research Institute (FRI) holds living examples, and in some cases seeds, of 120 species of trees. About 15 are of commercial interest, and a further 25 have commercial potential. The trees are mainly exotic, but some natives are included (Halloy 1995). New Zealand also has many ornamental plant collections, some of world importance, particularly for species under threat in their country of origin. The Royal New Zealand Institute of Horticulture (RNZIH) is keen to foster local networks and possibly a national network of exotic and native plant collections, including ornamentals. The Herb Federation of New Zealand (Inc) also supports a semi-formal network of collections of herb species and varieties (Halloy, 1995).

The main threats to non-commercial and unfashionable crops and livestock are the lack of facilities to keep live populations or store genetic material (i.e. seeds, semen etc.) and the lack of resources to properly document and authenticate them (Halloy, 1995). It is not known how much of the material stored in genebanks is still alive, though current management practices often appear deficient. Collections of minor crops, such as nuts, rare fruits, and ornamentals, are at risk. There is no national register to identify them and few collections are under institutional supervision. New funding would be required to ensure that all surviving cultivars are maintained. As there are many thousands of varieties stored in gene banks, and no way of knowing in advance which of these will be needed for future breeding programmes, the maintenance of such gene banks is essentially a public good.

There is an international dimension to our need for adequate crop and livestock conservation measures. As a signatory to the International Undertaking on Plant Genetic Resources (1983) New Zealand has agreed to maintain important genetic material and share it internationally (there is no parallel agreement relating to animals). The International Convention for the protection of New Varieties of Plants (abbreviated to the French acronym, UPOV) provides a legal framework which allows legal rights to ownership of plant varieties for a limited number of years. With its wide range of climatic and habitat conditions and a relatively disease-free environment, New Zealand is well-placed to even become a repository for exotic taxa whose future is insecure in their country of origin (Halloy, 1995). This may also apply to certain wild plants and animals.

However, the need to conserve desirable exotic biodiversity must be balanced against the need to control harmful species. Our 120 crop and forage plants, for example, are matched by more than 200 exotic weeds that threaten native ecosystems (Timmins and Mackenzie, 1995). In some cases, the helpful and harmful species are one and the same. Pasture grasses and pine trees are worth millions of dollars to the economy, but their spread has often been at the expense of native forests, wetlands and dunelands. Livestock, too, can cause damage by wandering into forests and wetlands and defecating near waterways. Conserving exotic biodiversity, therefore, must go hand in hand with vigilant pest and weed control and sustainable farm and forest management.