Impact of Humans on Biodiversity

The incredible expansion of the human race of the past few centuries has caused the extinction of many species of animals and plants. This mass extinction has been qualified as the sixth major extinction crisis. The difference of this crisis compared to previous one is that it has happened 1000 to 10 000 times quicker and isn’t showing signs of slowing down. In fact, it is still accelerating exponentially. It is also unique as it is down to the success of a single species, Man, which is creating the extinction of all others.

The changes Man is doing to the environment has unprecedented effects on the the abundance of different species, the ecosystem and on the genetic variation of different organisms. 

Causes of extinction

The primary causes of this erosion of biodiversity are of demographic, economic and institutional nature. Mainly, the increasing need for land and biological resources because of the growth of the human population, production, consumption and commercialisation of the world associated to the inability of people and markets to realise the long term consequences of environmental changes and values of biodiversity (Declaration of Paris on biodiversity, 2005).

The main causes are the loss and fragmentation of habitats, biological invasion, over-exploitation of species, pollution and climate change.
The factors act either separately or together, raising the risk of extinction. This is the case for example of species victim of habitat loss, and therefore weakened and will be exposed to human exploitation.

The extinction of a species can also be down to the extinction of other species that it depends on, this is called co-extinction. A prime example of this is that of the Iberian Lynx that was specialised in hunting rabbits and is now in critical danger of extinction due to the dramatically rapid drop in population of its prey. Over 6300 species are under threat in this way. In the long term, entire ecological systems could disappear.

Iderian Lynx extinct due to the impact of humans on biodiversity

The human factor

This sixth extinction crisis is unique due to its link to human activity and the growth of the human population which is putting pressure on other ecosystems and species. Currently, the planet is home to 7,5 billion people. The time it is currently taking to double the worlds population is only 35 years. If this continues on the same level, there will be 60000000 billion people on Earth in just 900 years. Meaning for every square metre of the planet, there will be 100 people.

This figure obviously won’t be reached. However, it means the impact man has on the world isn’t reducing and instead is growing faster than ever before.
Therefore, it is important to put an end to this impact.

Red list of the ICUN

Every year, the International Union for Conservation of Nature (ICUN) sends out a red list of endangered species. This red list makes up the most complete world inventory of plant and animal species. It is based on a number of precise criteria to evaluate the risk of extinction of thousands of species. These criteria are relevant to every species and every part of the world.

In 2006, 16 118 species were under threat. This total only takes into account species that were studied. This was about 40 000 out of a total 1 560 000 known at the time. 40% of all species studied by the ICUN are under threat of extinction and as only a small amount of all species were studied, the number is surely a lot higher than 16 118 endangered species.

Numbers of endangered species therefore are most definitely underestimated. Even more so as we still have only discovered a fraction of the entire biodiversity.  In fact, only 1,5 million out of an estimated 15 to 30 million species are known to us.

The ICUN has established many severity criteria. From them, we learn that 1 541 species are in critical danger of becoming extinct. 2 258 species are said to be endangered. 4591 are described as vulnerable. 

Remember that the ICUN red list has no regulatory value. Its aim is to direct the public attention towards this worldwide emergency. It also aims to create a momentum of willingness to change and limit the risk of mass extinction.

Culturing Aphids 2

During my visit to Sweden I was impressed with Lars Österdahl’s methods of culturing aphids. He maintains these on pea plants that are lit for about 16 hours per day. Lars soaks pea seeds for about a day before planting them in compost. Unfortunately the pea plants are not very robust and collapse very rapidly when the numbers of aphids increase. This means that new plants need to be started every fifth day, something of a chore.

It is important to choose the right species of aphid, as most are specific to a plant or group of plants. The ones used are the Pea Aphid Acyrthosiphon pisum. Each plant is seeded with a few pea aphids (though technically only one should be needed) and they can be harvested after about ten days by either putting the whole culture into the vivarium or blowing them off the plants into the vivarium. Cultures need to be protected from predators as the can quickly be decimated by just one Ladybird! The aphids are undoubtedly an excellent supplementary food source.

It is important that the plants and aphids receive at least 16 hours of light and I have lit mine with a 28W, low energy lamp (150W equivalent).

On my return I maintained my cultures on dried Marrow fat (mushy) peas that are extremely cheap from the supermarket. As they are intended as food, they are fungicide or insecticide free. I tried to keep them going but it was a problem due to the need to be rigorous in starting new cultures every fifth day and after a plant failure I lost the cultures.

We managed to acquire some more aphids from a UK University where they are cultured as a food for ladybirds in a research project. I found that they were being cultured on Field beans (Vicia faba). These are intended as green manure or fodder bean. The seeds, which are between the size of a pea and a bean, need to be soaked for three or four days, until a substantial root is evident before being planted. However, they are robust and hold the colonies of aphids well, though not quite such good numbers as those on peas. The aphids are introduced after the second leaves appear. As these plants are relatively slow growing, new ones only need to be started every two weeks or so. Lucerne should also provide a good plant source for the aphids. I will experiment with this and let you know how the cultures go.

I have found a source of these beans:

    John Chambers Wildflower Seeds,
    15 Westleigh Rd,
    Barton Seagrave,
    NN15 5AJ

Tel. 01933 652562

They cost £3 per kilo but unfortunately the UK postage is a further £3.40 (approx $US or €5 and $US 6 respectively). However 1kg should last a couple of years. Our overseas members should be able to find these locally.

At this time of the year I can easily collect in a few minutes the aphids that it takes a week to produce. In my case, they are not worth the trouble to culture. Winter is, of course, a different story. I intend to simply keep my cultures ticking over until autumn when I will re-start them to provide a more varied diet for my animals.

If you consider doing the same, I would suggest starting some plants in late August. Also, start collecting some aphids from the wild at about the same time.

Culturing Aphids

Every one who keeps Poison Dart Frogs knows how important is to aphidsfeed them with a good variety of different foods. We have standard foods such as small and large Drosophila, crickets, Indian meal worms etc. These insects are readily taken by frogs throughout the whole year, but during the winter frogs are fed only on these. I wanted to keep another food for them and decided on aphids, because culturing aphids is easy and frogs love them.

I will describe the culture of aphids using two colonies from which you can get a handful of aphids approximately every four days. 

In order to grow the host plants, you will need eight squat jam jars (approx. 500ml each), spruce (Picea) sawdust, beans (not common bean from your kitchen), 2 insect cages (wood or metal frames coated with a fine textile-like gauze or muslin) and a laboratory culture of aphids. Next, fill four of the bottles ¾ full with sawdust, add a handful of beans and cover them with another 2cm of sawdust.

Water each bottle with 200-250ml of lukewarm water and cover with a piece of glass.  Put them inside the insect-box near the window but out of full sun.  After 6 days add a further 100ml water in the morning. Take off the glass lid and add aphids in the afternoon.  After a further four days, water each bottle with 100ml and after another 4 days you can collect aphids for your frogs. It is simple to collect them – put a sheet of paper under the culture and blow on the aphids.  They will be dislodged and will land on the sheet of paper.   Temperature should be between 21°C and 30°C.  

It is useful to make small record labels for each culture.  For example, you might include: 
14.12. Tuesday – water with 200-250ml; 

20.12.Monday – water with 100ml in the morning; add aphids in the afternoon; start with four new bottles; 
24.12.Friday – water with 100ml; 
28.12. Tuesday – collect aphids.

Culture and Collection of Aphids

With spring approaching, the prospect of supplementing our frogs’ diet with wild caught insects becomes a reality. One valuable food source is the aphid. Catching or culturing these insects is possible and some methods are outlined here.

Culture and collection of aphids is hard work

Over 4,000 species of aphid have been described worldwide, the majority from temperate climates. In Britain there are several hundred species, each with its own particular life style and food plant(s). Some species are of huge economic importance and the subject of much research, as they damage plants by feeding in large numbers and transmit more plant viruses than any other group of animal. Most are host-specific, feeding on one or a few related plant species. Some alternate their life cycle on a limited range of specific and unrelated host plants depending on the season. Host plants are located using chemical and visual cues.

Despite their common name of greenfly or blackfly, aphids are not flies but belong to the order Hemiptera, sub order Homoptera, a group that includes cicadas, frog and leafhoppers and scale insects. All Hemipterans have piercing mouthparts to penetrate their host. Some, like the assassin bug, are predators of other insects whilst others, like the bed bug, are mammalian parasites. Aphids feed on plant sap. Using their long, stiletto mouthparts to reach the sap-conducting tubes (phloem tubules) deep within the plant tissue. On close inspection aphids have mouthparts within mouthparts. When individuals settle on a plant only the main “rostrum” contacts the plant surface. Supported within this structure are the “stylets”. These are long, flexible ‘drill-bits’ that penetrate the plant. They then seek the phloem tubules (microscopic tubes which carry food up and down plant stems), which they puncture to reach the plant sap.

The simplest life cycle is found in aphids that do not alternate between host plants. A typical one being as follows:

In spring, eggs laid the previous autumn on the host plant by egg-laying females hatch and a special type of female aphid called the ‘fundatrix’ emerges. These, which look different to later generations, have the job of founding the colony by producing the next generation of wingless female aphids. These are born alive and are produced parthenogenetically i.e. without mating. Through the spring and summer these females give birth to more genetically identical clones of themselves. Some species are prolific, with colonies growing rapidly. A reproductive rate of five young per day during the course of a month is typical. With the young reaching maturity within a week, the overcrowding and decline in host plant quality triggers the adult females to start producing winged female aphids. These take to the air to seek new hosts. Those that find a suitable plant start another colony of wingless virgin females. The colony survives through parthenogenetic reproduction of genetically identical winged or wingless females. The shorter days of autumn, reduced temperatures and reduced host plant quality stimulates the virgin females to produce a special egg-laying female together with males. These mate, and eggs are laid in crevices on the plant. The eggs are resistant to cold and in this form the insect over-winters before hatching the following spring.

Collecting Aphids in the Wild

Colonies of many different species are to be found on plants during the spring, summer and autumn. They can be collected using an entomologist’s ‘pooter’. This is based on a small-stoppered bottle and I use a small spice jar plugged with a demijohn cork. The stopper must be wide enough to enable two separate holes each about 8mm in diameter, to be drilled through. A length of flexible plastic tubing is pushed through each hole, one about 150mm long, the other about 600mm. A piece of muslin or similar netting is secured over the open end of the shorter tube (the end that will eventually be inside the bottle). The longer tube is also threaded through the cork with a small length protruding but the end is not covered. The fit between tube and cork should be airtight, and silicon sealant can be used to ensure this. Once the cork is fitted to the bottle you are ready to poot. Suck on the shorter tube whilst aiming the open end of the longer tube at an aphid or other small insect. The bug will be hoovered into the bottle but the muslin prevents it from continuing its journey into your mouth. By using a mass-produced jar, when it is full, and taking care to prevent escapees, you can pop the cork, replace the original lid, and begin again with another jar.

Culturing Aphids

Identifying aphid species is a job for experts in the laboratory and not to be attempted by the easily bored, but the correct plant to aphid combination is important. Cultures of aphids should be maintained on living, healthy plants rather than cut material. One way is to find an aphid colony on its host plant in the wild and to cover it with a cage. This could be based, for instance, on a clear plastic fizzy drink bottle which will protect the colony from predators like parasitic wasps, hover fly larvae and beetles e.g. ladybirds. One example of a suitable species for this treatment is the Rose Aphid (Macrosiphum rosae), which is the gardener’s “greenfly”. Colonies can be started by transferring females to other rose plant leaves, or to uninfected leaves of the same plant in order to ensure a supply of aphids. Stinging nettles and honeysuckle are also regularly colonised by aphids, and would be good plants to check.

To raise colonies under controlled conditions it is best to cultivate common garden pest varieties that you can transfer to the appropriate cultivar plants, avoiding pest-resistant varieties. One common aphid is the Black Bean Aphid (Aphis fabae). This, the gardener’s ‘blackfly’, is almost certainly the species referred to by Jan Stenicka in BDG Newsletter No. 36, January 2000, which forms large colonies on broad beans, sugar beet and dock. Bean plants can be grown in pots or in jars. Once these have grown, the aphids can be transferred on a small piece of infested plant. Colonies tend to break up once they become very overcrowded. Therefore, it is advisable to have enough plants with which to seed new colonies. Another species, the Cabbage Aphid Brevicoryne brassicae, does not appear to be taken well by the frogs. Colonies will need to be protected from predators/parasites and the simplest way to do this is to place the plants in a screen cage ensuring that enough light can get through to keep the plant healthy.

If you are able to keep the temperature and lighting levels high throughout the winter you may be able to keep your aphid colonies going on a succession of fresh host plants in a greenhouse. I have done this with one species (Aphis verbasci) on Buddleia. However, good lighting is essential to keep the plants healthy and actively growing.

Wetas back from the brink and breeding

Two threatened species of weta – found only in tiny pockets of the Tusked WetaCoromandel and King Country – have recently been discovered breeding outside their traditional habitats, thrilling conservationists involved in their plight.  The ferocious-looking Middle Island Tusked weta and the Mahoenui Giant weta were once feared extinct, but the latest findings have given renewed hope to their long-term survival.

Giant WetaSince then Doc has carried out extensive investigations and feasibility studies aimed at increasing the number of Tusked wetas and moving them.That is due to Conservation Department (Doc) recovery programmes, which date back 10 years.
The Tusked weta was discovered on Middle Island, part of Coromandel’s Mercury group of islands, less than 30 years ago.
  It was hailed as one of the most exciting insect finds of the century.

Jason Roxburgh of Doc’s Hauraki office told The Waikato Times this week there had been a breakthrough… Tusked weta had been recently identified on nearby Red Island.

“It’s an amazing achievement given that translocation (shifting) of other invertebrates to other islands hasn’t been overly successful.  It was a really steep learning curve… taking in a species we didn’t know anything about. Its behaviour is so different. It lives underground most of the time, which makes things difficult.”

The captive breeding programmed that had operated since 1993 was done in conjunction with Chris Winks of Landscape Research.  In 2000, Mr. Winks and Doc staff had released 150 weta on Double Island and Red Island, said Mr. Roxburgh.

Signs of breeding were first discovered in April this year.

“When they come above ground the females have egg spikes, which they poke into the ground, so we’d seen where they had been.”

The only way to confirm offspring was by constructing an inside enclosure.

“The guys found some eggs in them, then found some tiny weta,” said Mr. Roxburgh.  “It’s like a safety net. We’ve got two populations living separately, so we’ve got an insurance policy.”

The real celebrations were being saved for next year, however, when it was hoped a further generation of Tusked weta would be produced.

“That’ll be the true beginning of a new population,” Mr. Roxburgh said.

The Tusked weta would then be protected from being wiped out by an environmental disaster, such as fire.

Although the relocation programme for the King Country’s giant Mahoenui Weta on Mahurangi Island in Coromandel had shown no evidence of success, there was still hope. About 200 were set free on Mahurangi in 1996.

But Tertia Thurley of Doc’s Maniapote office said some Mahoenui giant weta had been successfully moved from the Mahoenui scientific reserve to a small block of gorse on private land.

That had proved the weta was capable of being moved.


Poisonous Customers hop to the aid of Peru’s forests.

An innovative frog-exporting business is a new departure for the private-Poisonous frog-exporting from Perulending arm of the World Bank, writes Demetri Sevastopulo, Financial Times (London, May 3, 2003, Saturday USA Edition 1)

They may not have studied at Harvard Business School but the International Finance Corporation’s latest recruits are doing more than their fair share to promote sustainable development. Decked out in vivid colours, the tiny amphibians at the private-lending arm of the World Bank are poison-dart frogs. Known as Epipedobates and Dendrobates, they are part of a business model to protect Peruvian rainforests.

The IFC and a local partner are establishing a frog ranching and export business. “We are promoting sustainable cultivation of poison-dart frogs for export so local people can earn a better living from conserving the forest than cutting it down,” said Sam Keller, the IFC officer responsible for the project. The move reflects a new trend in the way the IFC does business. Other projects in the pipeline include a catch-and-release eco-tourism fly-fishing venture in Mongolia.

“The IFC used to fulfil its mission largely by providing financing for private-sector projects in developing countries when few other institutions would do so,” said Mr. Keller. “But now we are trying to identify activities that provide environmental and social benefits while enhancing the bottom line.”

Using a technique developed by German biologist Rainer Schulte, fanners, or campesinos, attach half-cut plastic bottles to trees, filling them with water to create breeding pools in which frogs deposit tadpoles hatched from the females’ eggs.

Subsistence farmers can earn more selling frogs to pet markets than selling trees to loggers. Campesinos generally earn $50 a month but the IFC hopes to boost their income to $115. In the process, it estimates it can save 3,000 hectares of forest.

The genesis for the project came from Dutch biologist Jan Post, who stumbled on the potential of frogs. After buying his daughter five less exotic frogs, she bred them into 100 that she sold at an amphibian day in Baltimore, Maryland. “By 4pm she had sold the whole lot for $750.” Mr. Post noted that poison-dart frogs, more difficult to breed, fetched higher prices. He then developed the project, working with Mr. Schulte, before bringing it to the IFC to obtain finance. The project won the World Bank’s Innovation in the Marketplace award.

Sabrina Bimer, a biodiversity business consultant who did research for the IFC, said: “They (poison-dart frogs) range in price from $40 to $120.” Rarer species can fetch as much as $200. The largest market outside the US is Germany, where there are an estimated 10,000 frog enthusiasts.

Frogs & Forests, as the IFC-backed business is called, is steering clear of the seamier side of the trade in rare animals. Less highly principled entrepreneurs supply pet lovers in the developed world with protected species and have links with criminal networks.

Under the Convention on International Trade in Endangered Species, trading the frogs is only permitted as long as the population is sustained. The IFC estimates the trade in smuggled poison-dart frogs is as much as $2m a year. Mr. Keller said a benefit of the IFC project is that it would help reverse a declining population.

“We should be able to capture a fair amount of the legal market share and displace a considerable amount of the illegal trade because we are a low-cost producer and consumers prefer to buy legally imported frogs if they are available,” said Mr. Keller.

Poison-dart frogs are so named because of the tribal practice, which still exists in parts of Colombia, of extracting their toxin for darts that are shot from blowpipes to kill animals. The frogs can easily adapt to urban life. When removed from their natural habitat they lose their toxicity and pose no threat to their owners.