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Overgrazed area, by native fauna in western New South Wales, in the upper right corner.

Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, or by overpopulations of native or non-native wild animals.

Overgrazing reduces the usefulness, productivity, and biodiversity of the land and is one cause of desertification and erosion. Overgrazing is also seen as a cause of the spread of invasive species of non-native plants and of weeds.

Overgrazing is used as the canonical example of the Tragedy of the commons.^[1] Sustainable grassland production is based on grass and grassland management, land management, animal management, and livestock marketing. Grazing management, with sustainable agriculture and agroecology practices, is the foundation of grassland-based livestock production since it affects both animal and plant health and productivity.^[2]

Process[link]

Overgrazing can occur under continuous or rotational grazing. It can be caused by having too many animals on the farm or by not properly controlling their grazing activity. Overgrazing reduces palatable plant leaf areas, which reduces interception of sunlight and plant growth. Plants become weakened and have reduced root length, and potentially the pasture sod can be weakened although in many locales overgrazing results in an increased sod vigour dominated by unpalatable grasses. The reduced root length makes the plants more susceptible to death during dry weather. A weakened sod allows weed seeds to germinate and grow.^{[citation needed]}

Indicators[link]

One indicator of overgrazing is that the animals run short of pasture. In some regions of the United States under continuous grazing, overgrazed pastures are predominated by short-grass species such as bluegrass and will be less than 2-3 inches tall in the grazed areas. In other parts of the world, overgrazed pasture is typically taller than sustainably grazed pasture, with grass heights typically over 1 meter and dominated by unpalatable species such as Aristida or Imperata. In all cases, palatable tall grasses such as orchard grass are sparse or non-existent. In such cases of overgrazing, soil may be visible between plants in the stand, allowing erosion to occur, though in many circumstances overgrazed pastures have a greater sward cover than sustainably grazed pastures.

Rotational grazing[link]

Under rotational grazing, overgrazed plants do not have enough time to grow to the proper height between grazing events. The animals are turned into a paddock before the plants have restored carbohydrate reserves and grown back roots lost after the last defoliation. The result is the same as under continuous grazing: in some parts of the United States tall-growing species die and short-growing species that are more subject to drought injury predominate the pasture, while in most other parts of the world tall, drought tolerant, unpalatable species such as Imperata or Aristida come to dominate. As the sod thins, weeds encroach into the pasture in some parts of the United States, whereas in most other parts of the worlds overgrazing can promote thick swards of native unpalatable grasses that hamper the spread of weeds.

Another indicator of overgrazing in some parts of North America is that livestock run out of pasture, and hay needs to be fed early in the fall. In contrast, most areas of the world do not experience the same climatic regime as the continental United States and hay feeding is rarely conducted.

Overgrazing is also indicated in livestock performance and condition. Cows having inadequate pasture immediately following their calf's weaning may have poor body condition the following season. This may reduce the health and vigor of cows and calves at calving. Also, cows in poor body condition do not cycle as soon after calving, which can result in delayed breeding. This can result in a long calving season. With good cow genetics, nutrition, ideal seasons and controlled breeding 55% to 75% of the calves should come in the first 21 days of the calving season. Poor weaning weights of calves can be caused by insufficient pasture, when cows give less milk and the calves need pasture to maintain weight gain.

Ecological impacts[link]

Overgrazing typically increases soil erosion.^[3] Reduction in soil depth, soil organic matter and soil fertility impair the land's future natural and agricultural productivity. Soil fertility can sometimes be mitigated by applying the appropriate lime and organic fertilizers. However, the loss of soil depth and organic matter takes centuries to correct. Their loss is critical in determining the soil's water-holding capacity and how well pasture plants do during dry weather.

Native plant grass species, both individual bunch grasses and in grasslands, are especially vulnerable.

North America - United States[link]

In the continental United States, to prevent overgrazing, match the forage supplement to the herd's requirement. This means that a buffer needs to be in the system to adjust for the fastest growth of forages.

Another potential buffer is to plant warm-season perennial grasses such as switchgrass, which do not grow early in the season. This reduces the area that the livestock can use early in the season, making it easier for them to keep up with the cool-season grasses. The animals then use the warm-season grasses during the heat of the summer, and the cool-season grasses recover for fall grazing.

The grazing guidelines in the table are for rotationally grazed, cool-season forages. When using continuous grazing, manage pasture height at one-half the recommended turn-in height for rotational grazing to optimize plant health. The growth habit of some forage species, such as alfalfa, does not permit their survival under continuous grazing. When managing for legumes in the stand, it is beneficial to use rotational grazing and graze the stand close and then give adequate rest to stimulate the legumes' growth.

Africa - Sahel region[link]

• overgrazing consequences in region: 2010 Sahel famine

See also[link]

• Overexploitation

References[link]

External links[link]

• Western Watersheds Project

Follow-on is a term used in the sport of cricket to describe a situation where the team that bats second is forced to take its second batting innings immediately after its first, because the team was not able to get close enough (within 200 runs for a five-day match) to the score achieved by the first team batting in the first innings. It is applicable only in the longer (more traditional) two-innings-each match.

If the second team to bat scores substantially fewer runs than the first team, the first team can enforce (at their captain's discretion) the follow-on, instructing the second team to bat again immediately. In this case the sequence of batting innings will be first team, second team, second team and then (if needed) first team, so the second team is said to be "following on". This is in contrast to the normal progression of batting innings which is first team, second team, first team, second team.

This rules governing the circumstances in which follow-on may be enforced are found in Law 13 of the Laws of cricket.

The Follow-on has two major purposes. Firstly it helps prevent unnecessary play. If the first team to bat is winning after the other side has batted, and is likely to win even after the other side has batted again, there is no need for this team to bat a second time. If the team following on does actually pass the first team score, the first team can then come back for their second innings. Either way the length of the match is usually reduced and the chances of a drawn match are lowered.

Secondly, the vast majority of matches are time-limited (typically to five days) and if the first team is made to bat again, again scoring a high score, they may not have enough time to take 10 wickets in the final innings, resulting the match being a draw, even though one team could have scored hundreds of runs more than the other. The team batting first would face a very difficult tactical decision in its second innings — at what point should it declare and forfeit the remainder of its innings to preserve enough time to bowl the second team out?

Because cricket pitches deteriorate as a match continues, the follow on is not always enforced. This is because the team who enforced the follow on may be required to bat last, when the pitch is most difficult to bat on. If a team believes the pitch is still good (or has become good) for batting, they may elect not to enforce the follow-on; instead they will return to bat and increase their already existing lead.

Minimum lead[link]

The number of runs by which a team must lead to enforce the follow-on upon its opponent is determined by Law 13 of the Laws of cricket, which takes the length of the match into consideration:

• In a match of five days or more, a side which bats first and leads by at least 200 runs has the option of requiring the other side to follow-on.
• in a match of three or four days, 150 runs;
• in a two-day match, 100;
• in a one-day (two-innings per side) match, 75.

Where a match is shortened, the leads required to have the option of enforcing the follow-on are determined by how many days' (or part-days') play remain when the match starts. For example, suppose a match is scheduled for five days, but the first day is washed out because of rain. If the match then begins on the second scheduled day of the match, the team batting first needs a first innings lead of 150 runs or more to have the option of enforcing the follow-on. This only applies to time lost before the first ball has been bowled: if a five-day match starts on the scheduled first day but, say, the second day is completely lost, it still counts as a five-day match for the purposes of calculating the follow-on target.

Enforcing the follow-on[link]

The follow-on is not automatic; the captain of the leading team decides whether to enforce it. This is a tactical decision which the captain will (or should) make based on the state of the game, the apparent strength of the two sides, and the time remaining.

Conventional theory argues that the follow-on is almost always enforced. In his classic text The Art of Captaincy, Mike Brearley deals with the issue in a single paragraph and finds the advantages of doing so overwhelming.^[1] Certainly there are strong reasons for enforcing the follow on. The main reason is one of time. In two innings games, for a team batting first to win, it usually needs to dismiss the opposition twice. If it fails to do so, the game will end in a draw. Indeed it is a common tactic for a side which appears to be well-beaten to bat cautiously in its second innings and use up the remaining time so that the game does end this way. Enforcing the follow-on means that the trailing side takes its second innings earlier in the game and will therefore find it much harder to play for a draw by using up time. Another reason for enforcing the follow-on is the positive effect it can have on a team's morale, and the equal negative effect on that of the other.

However, there are several reasons for not enforcing. Firstly and most simply, it is tiring for bowlers to bowl for two consecutive innings, and it may not be as easy to dismiss a side cheaply in its second innings as it was in its first. Secondly, not enforcing the follow-on is a cautious but perhaps prudent tactic which prevents a team from losing. If the side batting first has a substantial lead on first innings, it can add to that by taking its second innings straightaway and either scoring enough runs and/or using up enough time to give the side batting second no chance of victory at all. While this does increase the chances of a game ending in a draw, it can also be demotivating for the side batting second to have nothing to play for. Finally, it is also usually considered a disadvantage to bat last, when the pitch has deteriorated by wear and there are more natural variations to its bounce and ability to take spin. A captain who does not enforce the follow-on avoids this risk, and allows his own bowlers to take advantage of the worn pitch.

In recent years there has perhaps been a trend against enforcing the follow-on in Test cricket. England captain Andrew Strauss has on several occasions adopted the cautious tactic of taking his second innings straightaway. It has, though, had some notable successes, for instance at Lord's in the 2009 Ashes series. Here, Australia were 210 behind on first innings but did not follow on; England batted again, set Australia a highly unlikely victory target of 522, and won the game easily. For their part, Australian captains Steve Waugh and Ricky Ponting were also notably reluctant to enforce the follow-on, although that was perhaps more to do with allowing Shane Warne to bowl on a deteriorating pitch later in the game.

Victories by sides following-on[link]

Although it is not impossible for a side following-on to win a game, it happens rarely. When it happens in first class games, it is a notable occurrence, with that match being remembered for many years afterwards. Australia have been the losing side on all three occasions where a following-on team has won a test match.

The 1894–95 Ashes[link]

In the first innings of the First Test at Sydney, Australia had scored a massive 586 (Syd Gregory 201, George Giffen 161) and then dismissed England for 325. England responded with 437, leaving them ahead by 176. However, at stumps on the fourth day, Australia were 113 for 2 and looked to be the winners. But heavy rain fell overnight (in this era, pitches were not covered between days of play), and next morning England's slow left-arm bowlers, Bobby Peel and Johnny Briggs, were all but unplayable. England dismissed Australia for 166, winning by 10 runs,^[2] and went on to win the series 3–2.

The biggest turnaround[link]

In 1922 at Edgbaston, Hampshire were bowled out for 15 in just nine overs in reply to Warwickshire's 223 in a 3-day match. Hampshire's total is the seventh lowest score for a completed first class innings. Hampshire were put back in to bat, and then famously scored a mammoth 521 before dismissing Warwickshire for 158 to win by a comfortable 155 runs.^[3] Hampshire's first innings total of 15 remains the lowest score for a completed innings by a winning team.

Botham's test — England v Australia, Headingley, 1981[link]

In 1981, England's Ian Botham was performing poorly as captain against the touring Australians. The Australian team was rated as second only to the great West Indies team of the time, and contained a formidable pace attack in the form of Dennis Lillee, Terry Alderman and Geoff Lawson. After a loss and a draw in the first two Test matches of the summer's six-test Ashes series, Botham resigned the captaincy.

Mike Brearley, the captain Botham had replaced, resumed the reins for the third Test, at Headingley. This started out very badly: Australia scored 401 (John Dyson 102; Kim Hughes 89; Botham 6–95), and asked England to follow on after bowling them out for 174 (Lillee took 4 for 49; Lawson 3 for 32). The one bright point in the innings came from Botham, who top scored with 50 (his first since he had been made captain 13 matches earlier). In the second innings, Botham came to the crease with England on 105 for 5, still 126 behind. Matters did not improve: Geoff Boycott and Bob Taylor soon followed, and with England 135 for 7 and still 92 runs behind an innings defeat looked likely.

By all accounts, everyone on both sides thought the game was lost. Ladbrokes famously offered 500–1 against England winning the Headingley Test. When Graham Dilley joined him at the crease, Botham reportedly said, "Right then, let's have a bit of fun." Botham, with able support from the lower order, went on to make 149 not out, and gave England a slender lead of 129. The next day a fired-up Bob Willis took 8 for 43, and Australia slumped to 111 all out.^[4] It was the first time since the 1894–95 Ashes that a side following on had gone on to win a Test match.

India v Australia, Eden Gardens 2001[link]

Australia, who had won their 16 previous Test matches, including the first of the three-Test series between the two teams,^[5] had scored 445 in the first innings of the second Test and restricted India to 171; only V. V. S. Laxman (59) and Rahul Dravid reached 25 runs. The only other bright spot for India was the bowling of Harbhajan Singh, who took 7 for 123, including a hat-trick (Ricky Ponting, Adam Gilchrist, Shane Warne). Australia then enforced the follow-on.

Laxman came to the crease just before the end of Day 3 and proceeded to change the course of both the match and the series by hitting 281, at that time the record for an Indian Test batsman. He did most of his damage partnered with Dravid, who hit 180; the two were at the crease for the entire fourth day. India progressed to 657/7 in their second innings (a lead of 383), and, surprisingly, there was not even a single six from the winning side in either innings, and then on the final day declared shortly before lunch (giving Australia insufficient time to reach the total, thus securing at least a draw). By tea, Australia had scored 161/3, and a draw appeared the most likely result. Then, within minutes, Australia lost five wickets for 8 runs in a span of 31 balls. Harbhajan took the first two wickets in the same over, followed quickly by three wickets from Sachin Tendulkar. Australia proceeded to fall for 212 in the second innings and India won the match. Despite Harbhajan's prodigious bowling—6 for 73 to go with his seven-wicket haul from the first innings—Laxman was named man of the match.^[6] This was only the third Test match (and last to date) to have been won by a side following on, as well as being the only time in history that a side has been able to declare the follow-on innings and still win. India went on to win the 3rd test, and hence the series, with Laxman contributing half-centuries in both innings and Harbhajan, who was named as man of the series for taking 32 wickets.^[7]

Longest period without being forced to follow-on in test cricket[link]

Longest period without being forced to follow-on in Test cricket is held by Australia, who after being asked to follow on by Pakistan in Karachi in 1988, went 190 matches without being forced to follow on until being asked to do so in the fourth test of the 2005 Ashes series against England.

The History of the follow-on[link]

• 1787 First known instance.
• 1835 Compulsory after a deficit of 100 runs.
• 1854 After a deficit of 80 runs.
• 1894 After a deficit of 120 runs.
• 1900 Made optional, after a deficit of 150 runs.
• 1961 In abeyance in County Championship. Restored in 1963.^[8]

Notes[link]

1. ^ Brearley, M. The Art of Captaincy. Macmillan, 1988, p.212
2. ^ 1st TEST: Australia v England at Sydney Cricket Ground, 14–20 Dec 1894
3. ^ Warwickshire v Hampshire at Birmingham, 14–16 Jun 1922
4. ^ 3rd TEST: England v Australia at Leeds, 16–21 Jul 1981
5. ^ "Test No. 1531 — Border-Gavaskar Trophy, 1st Test, 2000/01, India v Australia". ESPNcricinfo. http://www.espncricinfo.com/india/engine/match/63919.html. Retrieved 2011-09-23. 
6. ^ "Test No. 1535 — Border-Gavaskar Trophy, 2nd Test, 2000/01, India v Australia". ESPNcricinfo. http://www.espncricinfo.com/india/engine/match/63920.html. Retrieved 2011-09-23. 
7. ^ "Test No. 1539 — Border-Gavaskar Trophy, 3rd Test, 2000/01, India v Australia". ESPNcricinfo. http://www.espncricinfo.com/india/engine/match/63921.html. Retrieved 2011-09-23. 
8. ^ 1966 edition of Wisden Cricketer's Almanack, p153.