Chang­ing rain­fall brings more cat­tle pro­duc­tion to Ka­roo’s sheep re­gions

Justin du Toit, a sci­en­tist in pas­ture re­search at Groot­fontein Agri­cul­tural De­vel­op­ment In­sti­tute in Mid­del­burg, spoke to Roelof Bezuiden­hout about his anal­y­sis of rain­fall records in the Cen­tral Ka­roo and how farm­ers can adapt to cli­mate change.

Farmer's Weekly (South Africa) - - Contents -

How WOULD YOU DE­FINE A DROUGHT?

Long-term records al­low us to build a his­tor­i­cal pic­ture of drought in an area. This can be tricky as drought is in­flu­enced by many vari­ables, in­clud­ing the amount of rain­fall, its tim­ing, run-off, tem­per­a­ture and hu­mid­ity, sea­son and the en­vi­ron­ment. How­ever, be­cause these fac­tors are sel­dom prop­erly recorded, we mostly use weather data, no­tably rain­fall, to de­fine drought. Sim­ply put, drought is an un­usu­ally dry pe­riod.

Ar­guably, the best way to clas­sify an area as ex­pe­ri­enc­ing drought is by its ef­fects on the ground, such as crop fail­ure, scarcity of drink­ing wa­ter, fod­der short­ages, re­duced stream flow, and plant and an­i­mal mor­tal­ity.

Droughts are, of course, a fea­ture of semi-arid range­lands ow­ing to the high rain­fall vari­abil­ity typ­i­cal of such ar­eas. It’s small won­der that rain­fall is a key driver of ecosys­tem pro­cesses, es­pe­cially veg­e­ta­tion dy­nam­ics, in this type of veld.

With cli­mate change, parts of South Africa are pre­dicted to get wet­ter, oth­ers drier. Per­haps more im­por­tantly, vari­a­tion in rain­fall is set to in­crease, and the num­ber of rain days to de­crease. This in­di­cates a fu­ture of heav­ier show­ers when it rains, with longer dry pe­ri­ods be­tween rains. Here, as else­where, droughts and storms are pre­dicted to be­come more in­tense, the high­est tem­per­a­tures higher, and snow­falls greater.

Some re­search sug­gests that our win­ters will be drier; springs will be mainly drier but in some places wet­ter; sum­mers will be mainly wet­ter, ex­cept in the far west; and au­tumns will be drier.

de scri be your cur­rent re sear ch at the Agri­cul­tural De­vel­op­ment In­sti­tute

Some cli­mate change stud­ies pre­dict that the east­ern Ka­roo, and ar­eas to the east and north of it, will ex­pe­ri­ence in­creased rain­fall in fu­ture. Cer­tainly, the

rain­fall here in Mid­del­burg has gen­er­ally been higher than ex­pected for the past 30 years or so. Since the mid-1980s, the av­er­age an­nual rain­fall has been 430mm. Con­trast that with the 30 pre­ced­ing years when the av­er­age rain­fall was only 350mm.

If we look at the his­tor­i­cal rain­fall over the past 130 years or so for the re­gion, there is quite strong ev­i­dence of an ap­prox­i­mately 20-year cy­cle, and weaker ev­i­dence of a longer cy­cle. This 20-year cy­cle is well known, and if it holds true, we should be in a dry pe­riod at the mo­ment, with rain­fall in­creas­ing over the next 10 years. But these are only trends in av­er­age rain­fall; they are not pre­dic­tions of how much rain we’ll get from one year to the next. In the east­ern Ka­roo, rain­fall sea­son­al­ity has not var­ied much over the past cen­tury. Since the mid-1980s, rain­fall has gen­er­ally peaked in mid-sum­mer, just af­ter Christ­mas. Be­fore that, in the late 1960s and early 1970s, rains peaked later in the year, as late as mid-March or early April.

Lo­cal farm­ers also say that the rains are com­ing but at the ‘wrong’ time of the year. In the past, au­tumn rains were felt to be higher, and were very wel­come as they al­lowed the shrubs in the veld to green up to pro­vide fod­der into win­ter.

Mid-sum­mer rain, on the other hand, in­creases grass pro­duc­tion, some­times to the point where grasses ac­tu­ally out­com­pete the bossies [shrubs] and push them out of the sys­tem.

Rain­fall has also be­come more con­cen­trated in re­cent years; in other words the same amount of rain is fall­ing over a shorter sea­son. This is not use­ful for live­stock farm­ers, as they’d pre­fer rain to be spaced more evenly over the year.

Mid­del­burg lies roughly on the bound­ary be­tween the Ka­roo and the Grass­land Biome, and this bound­ary moves west and east de­pend­ing on rain­fall.

In dry times, grasses die out and shrubs thrive, and the bound­ary moves east. Dur­ing wet­ter times, grasses thrive and the bound­ary moves west. At the in­sti­tute, we have ex­am­ples of some ar­eas that were typ­i­cal bossieveld [shrub veld] in the 1960s, and have shifted to be­come grass­land with some re­mains of Ka­roo veg­e­ta­tion.

have these changes in­flu­enced farm­ing sys­tems in the ka­roo?

As veg­e­ta­tion changes, so do farm­ing prac­tices. The in­crease in grass has led to an in­crease in cat­tle farm­ing over large ar­eas in the Ka­roo. Where 30 years ago only sheep would have been seen, cat­tle are now a com­mon sight.

The early 1900s had the dens­est group­ing of very dry sea­sons. These were dif­fi­cult times due to the very low av­er­age rain­fall. Other pe­ri­ods dur­ing the cen­tury were also dry, at least in cer­tain sea­sons. For ex­am­ple, spring was very dry in the early 1900s, the 1960s had a clump of very dry sum­mers, and from 1980 to 2000 au­tumn was of­ten dry.

The high lev­els of vari­a­tion and com­plex causal fac­tors make it dif­fi­cult to dis­crim­i­nate be­tween nat­u­ral vari­a­tion and pos­si­ble ef­fects of cli­mate change on rain­fall.

In fu­ture, we’ll most prob­a­bly still have the same cy­cles that we’ve al­ways had, but their na­ture is likely to change to some de­gree.

What can farm­ers do to adapt to these changes?

It’s dif­fi­cult to give ad­vice to farm­ers on what to ex­pect and how to cope with cli­mate change be­cause of the huge vari­a­tion in weather pat­terns. That be­ing said, Aus­tralian farm­ers al­ready live with high vari­a­tion in weather. What we call a drought, they would call a tem­po­rary dry spell.

It may be use­ful for our farm­ers to see how their Aus­tralian coun­ter­parts cope, and per­haps con­sider adopt­ing their style of man­age­ment to some ex­tent.

Deal­ing with drought sim­ply by buy­ing in feed is un­likely to be the an­swer be­cause of cost. If pos­si­ble, it’s bet­ter to sell an­i­mals and then re­stock fol­low­ing the drought. Of course, the num­ber of an­i­mals that can be sold is lim­ited be­cause it’s im­por­tant to re­tain on-farm ge­net­ics.

One shift that a farmer could make is to re­tain more an­i­mals in good years and sell off more in poor years. This has the ad­van­tage of match­ing stock­ing rate to food avail­abil­ity, but the down­side of dis­rupt­ing herd and flock man­age­ment. It’s also prob­lem­atic in terms of cash flow and taxes.

Other man­age­ment strate­gies in­clude in­creas­ing fod­der re­serves (to my mind, spine­less cac­tus is the only real win­ner here in dry ar­eas) and low­er­ing the stock­ing rate. With the lat­ter, more food is avail­able to the an­i­mals, and the farmer is bet­ter able to push through a drought. De­creas­ing the stock­ing rate need not mean de­creas­ing pro­duc­tiv­ity; fewer an­i­mals per­form­ing bet­ter can be more pro­duc­tive than more an­i­mals per­form­ing worse.

In the US, some re­mark­able work has been done with breed­ing an­i­mals to eat less­palat­able plants. Hope­fully there is scope for this in South Africa, par­tic­u­larly if these species in­crease in num­ber in the fu­ture. • Email Justin du Toit at justin­du­[email protected]

‘ to my mind, spine­less cac­tus is the only real win­ner as fod­der re­serve in the ka­roo’

Roelof Bezuiden­hout

Rain­fall is highly vari­able in semi-arid re­gions such as the Ka­roo, and this largely de­fines the veg­e­ta­tion dy­nam­ics.

Justin du Toit

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