Today we are going to have the last lecture of this series it is the concluding lecture summing up analog system design. Let us see I would consider that every designer should know particularly analog designers are recommended that they should understand macro modeling very well. It refers to modeling a given system to the level of detail of concern to the application on head. So illustrating this for example let us consider an active device it did not be an op amp at all times but it could be transistor also. So in the first understanding of the op amp or transistor for example one has to understand about the most important thing in op amp is the feedback. So the op amp gain is of concern this gain has to be made okay very high in order that op amp can be usefully used. So input VI becomes equal to the output V naught because in this feedback system the loop gain is A okay. So V naught by VI is 1 by 1 plus 1 over loop gain so that 1 over loop gain says that it should be 1 over A. So this basic principle of voltage follower is fundamental to the aspect of most of our feedback systems. So the output is fully fed back to the input then output follows the input. So output follows the input is the basic principle output follows the input. So what is it that we have done we are now able to isolate the input structure it may be some source or transducer and this may be connected to the load. So any power can be delivered okay to the load using source which is not capable of driving that much power into the load. So this is a power amplifier. So the model used here is a simple voltage controlled voltage source okay or current controlled current source where it is a current follower with a certain gain that is just DC gain. So this makes us understand all about follower systems which are the characteristic systems that are used throughout the analog system design. It could be if it is current II and current II and output current okay is fed back and this is the current amplifier okay this is let us say current amplifier the output current. So again if this is A times I in output current by input current becomes equal to 1 independent of A. So the desensitization aspect of negative feedback okay linearization aspect of negative feedback all these things can be explained. The actually it is also next step is to improve the model so that you understand other concepts what is it even if this relationship between the input voltage VI-V0 and the output voltage in this active device is not linear that means A is not really a linear relationship between output and input voltage of this voltage control voltage source even then this follower action is produced that means we can next bring about a non-linearity okay in the device that is used as voltage control voltage source and show that in spite of that non-linearity this relationship is valid for incremental changes around any operating point and prove that over the entire range where the loop gain is very high this relationship of output following the input is valid. So that is my macro models are important okay and there is no point in including in the first instance itself the exact model for the device here and causing confusion to exist in terms of analysis etc. So the simplest model is the one that has to be used first in the system to good enough to make the basic principle get understood what is the basic principle? The basic principle is as long as the loop gain is high okay output is very nearly equal to the input. So this is making a system become linear desensitize it with most of the characteristics of the active device used inside okay. So the macro model therefore can be linear or non-linear it could be frequency dependent 0th order, first order, second order frequency dependence. So higher order frequency dependence can be progressively introduced to see the effect of higher order models on the performance of the system. In most op-amp applications which means in negative feedback applications of the active device is sufficient to use a model of VCVS with this kind of voltage gain. Now another thing is for example if an op-amp uses let us say 10 to 15 transistors and some resistors etc. Each device if it is modeled by its most complicated model including non-linearity frequency dependence etc. Then the number of nodes in the whole system keep increasing enormously particularly in VLSI systems this is going to be the case that micro model level of modeling is to be just used only at maybe it may not be necessary at all but if it is to be used it is necessary to be used only at the end after you understand okay each of the parameter of the active device influencing the system by bringing it one after the other. So for example for understanding the basic principles of negative feedback initially it is enough if you use a linear model okay and then understand and then see the limitations of the linear model and then improve the model by including the effect of let us say gain banded product for example instead of bringing in the effect of frequency in terms of large number of poles associated with the complex device like op-amp one could just bring in a first order okay frequency dependence and see the effect of the gain banded product on the performance of the feedback stage. So what happens in that case again in the case of op-amp one sees that the op-amp is approximated as an integrator with a gain of GB bias instead of A equal to A naught DC gain and then one sees the effect of this on the op-amp with feedback. So in the full feedback case it becomes now 1 by 1 plus 1 over loop gain which is going to give the transfer function between V naught and VI as 1 by 1 plus S by GB. Now that is a measure of the bandwidth up to which this system gets used. So the loop gain has direct influence on the bandwidth of the feedback structure that is what we are concluding from that. So it becomes a measure of the range over which the device is useful frequency range over which the device is useful. Now apart from this the saturation states where the op-amp no longer can be considered as an active device because the gain is 0 that is for a change in input voltage output change is 0 that is what the saturation state is. So that model has to be brought in to understand the effect of saturation states step by step that will limit the region over which this V naught following VI is valid or it will give the dynamic range over which this is functioning okay so called lock range right. So this is the case with most of the feedback systems that we are going to consider right it is going to work okay with all these equations getting valid only if within the lock range okay within the range of the dynamics possible for the circuit. Now apart from that non-linearity we have another functional limitation of the active device so that is nothing but the maximum rate at which output can change because these are using capacitors etc may be at the output or in feedback okay the rate at which the voltage can rise across the capacitor is limited by the maximum bias current okay that can go through the capacitor so that is limited. Therefore the op-amp can only work up to the maximum rate which is delta V naught by delta T max this low rate the consequence of this is that an output signal which is let us say should be sinusoidal okay for a sinusoidal input okay the output let us say is VPO sin omega T okay then the delta V naught by delta T expected is going to be omega VP naught cos omega T. So maximum rate at which output has to rise in order to be free from the distortion is omega into VP naught. So omega into VP naught in all these circuits must be less than or at most equal to the slew rate that means omega up to which this system can be used okay with the peak sin of VP naught is slew rate divided by VP naught or F max is always equal to this has to be verified before proceeding with any experiment okay. So this is the precaution that one should be that this if this is not incorporated in the model okay particularly at high frequencies maybe much less than the gain by the product of the op-amp itself this limitation will come into picture and people may just not notice this distortion happening and measurements will go become inaccurate one such a classic example is one if one is making a measurement of the gain bandwidth product itself. So the signal output should not swing okay at any frequency okay to an amplitude greater than what is limited by this. So that means at any frequency you are likely to calculate this VPO should be less than or equal to slew rate divided by 2 pi F okay corresponding to that. So this is an important limitation which normally people tend to forget it is enough even if you are dealing with higher order systems is most of the time enough okay will come to the restriction to second order in overall system design. All analog signal processing systems can be designed using active second order analog slash digital subsystems as building blocks okay. Now digital subsystems may or may not come into picture okay we will discuss digital by that we mean there may be certain amount of switching etc taking place okay in an analog system itself because like switched capacitor filters okay pulse width modulators etc. So second order analog subsystem is realized using op-amps as active devices and resistors and two capacitors as independent capacitors that means most of these systems whether they are analog systems or complex mixed mode systems or even electromechanical systems all systems today can be modeled as a sort of cascading of second order analog subsystems which use may be op-amps and as active devices and resistors and capacitors okay along with the op-amps. That means basically this analog computer modeling which was prevalent before the digital computer committee existence particularly in simulation of anonautics okay and mechanical systems okay as made a comeback in the form of its availability in terms of op-amps being made available okay and the facility of state space filter in simulating a simple second order system okay. So the analog computer simulation which has been used for long for even non-linear differential equation solution etc has made a comeback in the form of the availability of op-amps and systems like state space filters being made available. A digital subsystem is made up of ADC DSP and DAC then that means one can incorporate such a digital system okay in order to control the analog front and back end like filters okay and analog multiplexers can be controlled by DSP okay and the backend power amplifiers pulse width modulators switch mode power supplies all these things can be controlled okay by using DSP and such subsystems of course take a lot of time for the control so such digital control of analog system is what is prevalent today okay because of the ready availability of DSPs at low cost which are conveniently usable for controlling these analog subsystems. And the other advantage is the controllers integral controllers etc that request large valued capacitors okay for causing dominant poles to exist in the loop okay can be simulated using digital processors and delays cost in the processing okay can be cumulatively added to form large delays and lags. So these are all parts of modeling that we can take into account in understanding system design any analog system is functionally a filter. So particularly these linear systems can always be modeled as a filter that means an amplifier a wide band amplifier by itself is going to do filtering because of the fundamental limitation of what is a gain variation with respect to frequency right gain always falls at higher frequencies. So a second order system can be represented by a transfer function with a second order polynomial in S as denominator and the numerator that can be constant S term S square term and or the combination of all these terms in the numerator. So basically therefore we have most often this can complete all systems are basically looking like low pass filters. Some systems can be high pass filters of second order right and some will be okay band pass filters of second order right. So this refers to let us wide band amplifiers okay and also narrow band amplifiers okay. So and all these wide band amplifiers and narrow band amplifiers or draw band selective amplifiers all these things can be divide designed by cascading okay successive staggered peaks okay if it is low pass for example that we had already seen a maximally flat characteristics for this low pass can be got by cascading a first order low pass with a second order or higher order okay. So this is the way you can build higher order low pass systems. Again a band pass systems can also be built in a similar fashion you can build them using higher order and make them maximally flat okay by cascading together these staggered tuned amplifiers. So so on and so forth. So that is basic understanding in all these cases is that right it should be having a basic building block which is clearly a second order with a first order maybe. So these are other things that same thing is applicable for a band stop right you might have okay a thing like this notch or if you want broader notch right you may be having it something like this. So so on and so forth right higher order. Now it has also been seen in the present day technology that the analog parameters like resistance value or capacitance value okay. These are fundamentally sort of components whose value varies considerably as poor tolerance depends upon temperature etc. Right only ratios can be perhaps used fairly accurately okay to an accuracy which is better than that of the absolute values. So one must try to design systems which depend only on ratios of components rather than absolute values. And that is the attempt in present day design as far as analog systems are concerned otherwise further accuracy can only be obtained by digital signal processing okay and the analog system today is primarily used for high speed signal processing activities like in communication okay. If one has to use precision at that point of time precision is mostly locking and lacking in these particularly at high frequencies because parasitics become dominant at that frequency and maybe one has to use parasitic components themselves as components for signal processing application in which case one might have to tune these systems to the accuracy that we need by proper sort of feedback tuning control systems which are primarily DSP based control systems. So digital tuning of analog subsystems okay become absolutely necessary. So the initial need design need not be very accurate but when that should be provisioned to vary the various parameters involved by a wide range in order to tune precisely to the accuracy that we need. That is why tuning procedures for for example filters was thoroughly discussed and self tuned filters were also understood in the context of precision that is required. Higher order analog systems passive components in high frequency analog systems can be in the range of parasitics that is what I mentioned. So cleaning becomes part of day to day activity in signal processing. As the parameters drift with temperature there might be requirement that this tuning circuits themselves might be part of the system which is integrated into it okay. Now negative feedback is one important concept that is conveyed in analog signal processing very okay. Negative feedbacks makes the performance of the system less sensitive to variation in values of parameters associated with the active device okay. In which case actually the full feedback okay the full output being fed back to the input okay and output following the input is the procedure that we resort to in most of the feedback systems wherein we are not able to trust the accuracy of components used within the loop okay. It may be having two blocks okay or three blocks it does not matter. As long as the output is fed back to the input output follows the input if the sensitivity of the blocks within product of the sensitivities of the blocks within is what is called as loop gain is much greater than one that is all that is required. They need not be linear they need not be independent of temperature they can be frequency dependent. But output follows the input as long as the product of the sensitivity factor remains in all these regions of operation okay much greater than one. So voltage followers current followers phase followers frequency followers okay digital data followers okay you can have a D2A converter and A2D converter. So then digital data at the input is followed at the output. A classic instance of this is where digital is converted to analog analog is converted back to digital okay.  So this is the summing point at the integrator so that is the classic topology of this ignore delta modulator. So higher order feedback systems have always this issue of instability coming into picture and therefore if one has to have feedback to desensitize the performance factors with respect to the parameters associated within the loop then it better be having only an order which is second order or if it is higher order the attempt is made to tune the feedback loop such that it becomes second order that is called frequency compensation. So all higher order the second order systems when they are coming to be there may be control systems the like voltage regulators okay current regulators or the speed regulators or what is that AGC, AVC or amplitude stabilization or phase lock loop any of these okay the queue of the system if they are thought of as second order systems the queue of the system is kept equal to one if it is transient response that is of interest. So that there is just one peak okay and it quickly comes back to steady state if it is a step input for example. So this is followed in voltage followers current followers or phase followers or phase frequency lock loops okay. So that is the case with these control systems if it is steady state response frequency response that we are concerned then we should not let it peak if it is a second order and therefore it is constrained to be maximally flat that this queue is equal to 1 by root 2. So if it is not the magnitude response which has to be flat but it is the delay that has to be flat queue for a second order system is 1 by root 3 right. So these are the variants that are possible okay when actually we are designing filters also. So whether it is filter design okay or amplifier design or control system design the same rule of thumb is what is followed okay. All higher order analog systems are designed through cascading second order system that we have already explained. Now particularly very high frequency high speed systems like RF and microwave systems always require total avoidance of feedback intentional or an intentional right. So that is for them to work satisfactorily okay otherwise there is instability. So please remember that you design high speed systems by avoiding feedback we come to this point of low pass filters for example. So a low pass filter is basically first order low pass filter is in R and C. So it is transfer function is 1 by 1 plus SCR this we topic we have already discussed in filters but most of the systems to a first order frequency dependence can be treated as a low pass filter that is even an amplifier is a first order low pass filter first without feedback okay. So with this feedback this remains the same as first order but bandwidth of usage increases. A second order filter they had seen so the parasitic resistance which is normally associated with the transmission line okay between one node to the other node you can consider it as a resistance centered by a capacitance at the output okay. So this is the cumulative effect of a transmission line from one node to the other. So this is the interconnect the approximation to the interconnect is an R in series and a C in short like a low pass filter. So probe of course we have a resistance attenuator here and it will have a capacitance there. So we have lot of practical design applications of these filters okay in the actual design of electronic systems. Then we have also the attenuator which is nothing but a R to R ladder scheme which is a passive component okay and the parasitics there will cause delay. Now this important approximation in the modeling of such interconnect pattern okay it can be modeled as a higher level higher order system with R and wire inductance being taken into account and this hand capacitor. So it is an RLC low pass filter of second order and second order transfer function is already known to us. That means it might for a step input like a digital word coming here might cause that digital word okay to ring like this. And the ringing frequency and Q these are determined by this same omega naught and Q that we have earlier used in second order low pass filters. So the amplitude of this ringing may be such that this is going to trigger our digital circuit many times intentionally right. So this is the problem with this kind of interconnect response. So what has been therefore taken in the modeling is primarily the delay involved from transmission of the information from one node to the other. That is normally thermal as modeled as almost delay. So this is the thing interconnect is any connection between the two points in an electronic system. So that is modeled for example A to B RLC B to C another value of RLC depending upon the length and okay R3 L3 C3 like that it can go on. So how to model this? The ideal delay is modeled always as E to power minus S thaw where thaw is the delay. And this is important for the digital design particularly in high speed digital design this becomes very important criteria in designing such digital systems. So the analog man might like to approximate it better but the digital man wants to primarily know what is the delay caused by this complex network. This E to power minus S thaw is approximated as 1 by 1 plus S thaw plus S thaw square by 2 factor and so on. That means this is approximated okay as 1 by 1 plus S thaw. The coefficient of S whatever be the complexity of the circuit involved has been assumed as almost delay. So for example when the network is from note to note approximated as this kind of RLC network then the almost delay thaw the coefficient of S can be quickly calculated. This C1 into R1 okay as far as SC1 is concerned as far as C2 is concerned the C2 into R1 plus R2 the resistance connecting input to the node C total resistance R1 plus R2 then C3 into R1 plus R2 plus R3 so on okay. So you can quickly conclude that the almost delay thaw when such cascaded networks N such cascaded networks are there simply C1 R1 plus C2 to R1 plus R2 plus C3 into R1 plus R2 plus R3 plus CN into R1 plus R2 plus R3 plus Rn. All higher order systems can therefore be simply approximated as equivalent to giving a delay to the digital word by an amount thaw equal to this. So this kind of approximation helps a lot in understanding a complex system design and this is what has to be learnt from analog or this is nothing but the networks okay knowledge but it has to be emphasized in the beginning itself to the student and these are the topics of relevance today in electronics that must be emphasized in the beginning itself. So band pass filter so basically an interconnect or a connection from one node to the other as a resistive component and an inductor okay and then there is a shunt component coming there and therefore all these things can act as a resonator block and resonate and may therefore cause okay resonance at omega naught equal to 1 over root LC that is really dangerous because something that looks like a short circuit particularly let us say electrolytic high valued polar capacitors which may act as basically inductors at very high frequencies with some resistance in association with it can act as a resonant circuit and they may not act as a short circuit at all they will act at that frequency as open circuit in contrast to our assumption that this is the case with our power supplies which require huge bypass capacitors or holding capacitors okay which may turn out to be inductive okay at high frequency that is why most of these capacitors are further bypassed electrolytic capacitor has to be always bypassed by non-electrolet good quality capacitor which truly acts as a short circuit at high frequencies. So these are the things that we learn from learning to understand second order systems okay. Now amplifiers with negative feedback we have seen can be considered as basically second order system instead of first order systems and we can also decide about the second pole okay properly so that the queue of the system becomes equal to 1 this is called frequency compensation of the feedback amplifier and the compensated amplifier for delay compensation if an amplifier is going to be used in feedback the most important thing is not the flatness of magnitude or anything okay or may not making the queue equal to 1 or anything it may be that the delay component can be compensated for by having the same delay in the numerator or 0 in the numerator so that the order of the system remains the same but effective delay is minimized for this plot. So this is what is done when an amplifier is put in a negative feedback loop as part of the component it is delay compensating the amplifier which itself is used in negative feedback. Now filter yeah in filter design again the emphasis is on understanding the second order very well and the second order building blocks like state space filters are the most common building blocks of complex filters in analog today. Oscillator is nothing but a second order system simply with queue going to infinity and it oscillates at omega not equal to 1 over RC. So again stabilization of amplitude is another feedback system which can itself be first order or second order and can be optimized for its own control loop performance. So one of the complex systems that we have designed today is after all these classes we have designed quadrature oscillator okay and made it voltage control oscillator and then cost stabilization of amplitude of that oscillator. So we have involved ourselves with a very complex feedback system why for quadrature oscillator we needed integrators two integrators. Integrator itself is a negative feedback system that means basically this can be a second order system. So this second order system cascaded with further such systems was used in negative feedback to generate an oscillation that means this is a second order system this is second order system this is a third second order system. This has become a second order because there is a first order effect due to capacitor and there is the second order effect due to the GB. So this also is a second order this also is a second order. However when it is used in this loop we have understood how this has to be approximated as a first order with an error delay. This also has to be approximated as a first order effect with delay. This also is having a delay and cumulative delay is what causes Q enhancement of the system okay. So that is what is thought of in this system and we had made it voltage controllable by putting multipliers voltage control and then we had used squarers to add these outputs okay and get a DC dependent upon the amplitude of oscillation and then control the feedback factor here okay. So this is where we had introduced a multiplier and control the feedback and therefore that was a control system which itself can be a second order. How to understand this total system therefore taking care of voltage control frequency and stabilization of amplitude etc is only by making the models of all these things simple when we are considering the whole system. Then understanding first maybe stabilization okay then going into VCO operation then the oscillation of the system with Q equal to infinity. So these are the things to be done step by step bringing in complexity only step by step. The PLL has been modeled as again a frequency follower with transfer function equal to 1 by 1 plus S by omega naught Q plus S square by omega naught square. This again can be compensated using the same technique that we have used that means the low pass filter if it is just used okay the Q may be too high okay then one can introduce a 0 okay apart from this pole a 0 can be introduced here okay and the 0 is going to be just 1 plus S by omega Z divided by 1 plus S by omega P omega P is now equal to C into okay 1 by R Z plus R P omega Z equal to 1 by C into R Z. So one can therefore locate the 0 in the loop gain and make the Q equal to 1 if the original Q is very high that is what is called frequency compensating the phase lock load okay noise will therefore come into picture that means the double the frequency component for example will increase in its amplitude the moment is 0 comes into picture. So these are the basic design techniques of most of the systems that we have discussed so far finally okay what we can summarize is starting from the passive filters going to the amplifiers active filters oscillators all other negative feedback systems like DC regulators AGC ABC amplitude stabilizer oscillators PLLs and FLLs are designed as second order systems. So it is not something that has not been sort of said earlier but one has to realize the fact that these are all basic things which can be taught at fairly early state or assimilated early by our undergraduate students. So next comparators are used okay this is another category. So far okay whatever we have discussed we have discussed only basically analog systems comparator the moment comparator comes into picture comparators are used as interface components between analog and digital systems. Positive regenerative feedback is used in comparators to bring about hysteresis. So what is this hysteresis the hysteresis make sure that the active device is always used as a switch. Now this whether is a BJT or a MOSFET that active device is used as a switch that means particularly in power circuits we would like to use the active device okay for efficiency sake as a switch. Then it is necessary to drive such a circuit using comparators with hysteresis. So that is regenerative positive feedback speed trigger. A comparator is a 1 bit 8D converter an integrator with comparator can form a function generator loop that is the other mix this is the most important mixed mode circuit that we have discussed as a function generator. So it is used in almost all test oscillator circuits right and also in most of the VCOs okay currently used this is the topology that means current charging a capacitor okay and that is an input to a speed trigger with regenerative positive feedback. So this in fact if we have an analog input here right the output is going to be pulse width modulated here because of the analog input here okay. So this is similar to the basic concept of sigma delta modulator which is used particularly in data converters. So this kind of modeling okay this has to be modeled most of the time in time domain because of this non-linear element which is a regenerative comparator input is analog output is digital high or low. So comparators are also used in pulse width modulators duty cycle generators DC to DC converters and class D power amplifiers and switch remote power supplies where the active device is mostly used as a switch okay. So this aspect of understanding both comparators and op amp and multipliers. So these are the 3 basic building blocks along with as may be power devices the mass power device okay. So these are the ones that have to be given as basic components in laboratories to understand all these concepts very well. Where do we go from this course it is necessary that the basics in analog and mixed mode have to be thoroughly understood taking the topics and the components that we have listed earlier and analog IC design which is going to become increasingly specialized job okay and designing op amp designing comparators designing multipliers and designing the various ICs that are commonly used okay that has to be restricted as an elective or a higher level higher semester course okay and a follow up activity okay is particularly in power electronics for a switch mode power regulator design for large power and good efficiency and reliable operation is an important aspect of power supply management. So that has to be understood very well so then specialization for communication most of the analog signal processing is going to be restricted to communications. So one has to understand the RF electronics very well in understanding communication circuits and also microwave circuits again this is part of communication area. So these are higher level courses which may be electives I hope that this definitely must be made compulsory these three things can be kept as electives that is a recommendation right. Thank you very much for giving me an opportunity to say something about what must be done in analog today.


Vast areas of sub-Saharan Africa are home to the Cessiflai, a small but deadly killer. Cessiflai's transmit parasites called trypanosomes. These parasites cause human sleeping sickness, which afflicts thousands of people every year killing men. They also cause the livestock illness called trypanosomiasis, arguably Africa's most important livestock disease. Since no vaccine exists, the disease wastes and kills cattle across the region, holding back agriculture as a whole. After more than a century of work to control this disease, current methods remain difficult because they're expensive, toxic or unsustainable. With Kenyan and international partners, the International Livestock Research Institute, ILRI is now in the early stages of a project to develop cattle resistant to the trypanosomiasis parasite.  The project has identified the gene segment that protects the baboon, is making synthetic copies derived from this gene segment and is testing them in mice and sheep before using them in cattle. The team has already successfully adapted cloning methods. And next step is to produce African Boran cattle clones, modified with the gene segment originating in the baboon that confers resistance to the disease. A final step will be to use these trypanosomiasis resistant cattle in breeding schemes, which will provide Africa with a new option in its age-old fight against this lethal disease. This is a long-term research project. The first improved breeding herds may be available in 20 years, at which time decisions and regulations on their use will be determined by African countries themselves. If successful, this research promises for the first time a reliable, self-sustaining and cost-effective way of protecting African livestock against trypanosomiasis. The results will reduce poverty and hunger and enhance human well-being across the continent.


So, welcome to this session on Defending Nature's Last Frontiers. My name is Nicole Schwab. I'm with the Campaign for Nature at National Geographic Society, and I'm delighted to be introducing this session, and we'll be hearing from Enric Salin, who is an explorer in residence at National Geographic. Enric is a scientist who had been doing a lot of work on marine science and one day found himself riding the obituary for the oceans. And he decided that he was going to leave academia and dedicate his life to conservation. Over the past 10 years, under Enric's leadership, the Pristine Seas Project has created 21 marine protected areas, covering an area half the size of Canada. And today, this is scaling up. We are at a time where we have to accelerate our efforts to protect the Earth's last remaining wild places, to protect the ecosystems that we all depend on. And so I'm delighted to invite Enric to tell us more about Defending Nature's Last Frontiers. Thank you. Thank you, Nicole. Thank you. It's good to be back in the country that's home to the mighty Yellow and Yangtze rivers. But as our hosts know well, the Yangtze was a little too mighty 20 years ago. In the summer of 1998, it rained heavily. For over six weeks, water poured over the banks of the Yangtze, destroying everything on its path. It was one of the worst floods in modern Chinese history. By the time it was over, many homes were lost, many lives were lost. Authorities set out to understand what was the cost of such destruction, because many people remembered worse storms that caused less damage. And it didn't take them long to figure out what happened. In the years leading up to the flood, prosperity had come to the country, causing development that disrupted the balance between people and nature. To meet the needs of a growing nation, upstream forests had been cut down, and grasslands had been overgraced, which destroyed the ability of these ecosystems to absorb the excess water. At the same time, to meet the increasing demand for housing, people had been building homes and communities over wetlands, which are a great natural buffer against storm surges. Because in large part of the loss of these ecosystems, the Yangtze 1998 floods cost $20 billion in damages, and more than 3,000 lives were lost. One of the things I love about Chinese culture is that its major spiritual traditions, Taoism, Buddhism, Confucianism, reveal balance. They all teach the importance of living in harmony with nature and all living things. And that teaching is more important now than ever before, because the devastation, the loss of ecosystems that we saw in 1998 in the Yangtze are happening at a global scale. That means that we are risking similar types of devastation. And we can boil it down to one thing. Our planet is becoming less wild. We are totally out of balance with nature. And unless we get our balance back, human society, as we know it, is going to be short-lived. Let me give you an example of this imbalance. Today, 96% of the mass of mammals is us and our domesticated livestock. Only 4% is everything else, from elephants, to tigers, to panda bears. 70% of all birds are now domesticated poultry, mostly chickens. And in the oceans, 90% of the large fish have been extracted by fishing in the last century alone. Yet only 7% of the ocean surface has been designated or proposed as protected areas. And only 2% of the surface of the ocean is fully protected from fishing or other activities. We are doing a little better on the land, yet only 15% of the land is in protected areas like national parks or nature reserves. That means that ecosystems around the world are under serious threat. Now let me give you one example. The Amazon. The Amazon forest is one of the richest and most productive regions on the planet. It is so rich and diverse that you can find more species in a single Brazil nut tree than in an entire hectare of European soil. And one of the reasons for this richness is that it gets such heavy rain. And here is an interesting thing about this rain. The forest creates a rain. Trees absorb water from the ground and in the tropical heat release it as water vapor through the leaves. That water vapor will rise, eventually condense and fall as rain, which lowers air pressure, drawing in more moisture from the Atlantic Ocean, which will fall as rain and it will get into the ground and the forest will absorb it and so on and so forth. But now we are destroying the Amazon forest at the highest rate in recent decades. The equivalent of two football fields per minute. One study suggests that if we cut down more than 20 percent of the current Amazon forest, that cycle will break. The forest will not be able to produce enough rain and it will turn into a savannah. And that will affect the entire planet. There is a moral argument, clear moral argument against this type of devastation. But let's stick for now with the economic argument. The systems and the species that live in them are our life support system. It is these other species that produce the oxygen that we breathe. They pollinate our crops. They filter the clean water that we drink. They protect us from devastating floods. And wild places are the single best hope against climate catastrophe.  But we already have these technologies. Our forests, grasslands, wetlands and ocean habitats absorb half of the excess CO2 that we expel into the atmosphere every year. Of intact wild places, it will be impossible to achieve the Paris climate goals. Yet we are systematically destroying these ecosystems. The environment, our natural capital, every year provides $72 trillion in free support to the global economy. To put that into context, imagine that we combine the GDPs of China, the United States and Japan. Now double the number. That's how much value we get from the environment every year. But our overuse of natural resources are costing us $6 trillion per year and the number could go up to $30 trillion by 2050. A world above two degrees Celsius is not insurable. The CEO of one of the big insurance companies said that. That world without wild places is not even investable. The good news is that protecting ecosystems can provide greater value than destroying them. We just need to give ecosystems the space they need to recover from our abuse and continue providing for us. And I know because I have seen it. Now let me give you an example. In 1999, this little place called Cabo Pulmo in Mexico was an underwater desert. The fishermen were so upset with not having enough fish to catch that they did something that nobody expected. Instead of going out and trying to catch the few fish left, they decided to stop fishing completely. They created a national park in the sea, a no-take marine reserve. We went back 10 years later, and this is what we saw. We saw it go from degraded to pristine in just 10 years, including the return of the large predators like the groupers, sharks, and jacks. And you know who else is driving? Those visionary fishermen who are now making more money from tourism inside the reserve and better fishing around it. And I've seen similar examples around the world. On average, the biomass of fish is six times larger inside reserves than outside. And the economic benefits from tourism can be enormous. The Great Barrier Reef Marine Park brings in $5 billion to the Australian economy every year. That's 35 times more than fishing and many more jobs. And in the United States, every dollar invested by the US government on our national parks produces $10 in economic revenue to the local economy. The problem is that we don't have enough protected areas. So how much of the planet we need to protect? Studies suggest that if we want to avoid the extinction of one million species and all the benefits they provide, if we want to avoid the collapse of our life-support system, if we want a world not exceeding two degrees Celsius, we need to go renewable in terms of energy, but also we need to use half of the planet in a more responsible way and keep the other half in natural state. And to achieve that, we need to commit together to protect 30% of our planet by 2030. The People's Republic of China has embarked on an ecological redlining exercise and committed to protect a quarter of its lands and 30% of its coastal waters. That's an area larger than Greenland. These are ambitious targets, but some will say it's impossible. Why? Because we need more land and we need to fish more to feed 10 billion people. But we already produce enough food for 10 billion people. We just waste a third of it from the field to the table. And we make other senseless decisions along the way. If we just became a little smarter about the way we eat and produce our food, we could have both a healthy planet and a healthy food supply. But some will say, oh, it's impossible. It's going to cost too much. We cannot afford it.  Studies show that protecting 30% of the planet would cost on the order of tens of billions of dollars. And guess what is the price of subsidies for fossil fuels? Every year, governments subsidize the fossil fuel companies directly, pre-taxed with $300 billion. Plus, we need to add $5 trillion with which society subsidizes the cost of burning fossil fuels every year. That's numbers from the International Monetary Fund. The money is there. We just use it to fund the activities that destroy our natural capital, that destroy our life support system. But you know the really good news? That protection generates more value than destruction. New York decided that instead of spending $10 billion, building a wastewater treatment plan to produce clean tap water for the city, the city decided to spend only $2 billion protecting the natural water supply, the cut skills, the mountains, and forest north of the city. And now, New York has the reputation of having the cleanest and most drinkable tap water in any large city in the United States. That's the same value realized by the Chinese government after the 1998 floods. Realizing that future rains could create similar types of devastation, local authorities brought in environmental scientists to help restore the ecosystems along the Yangtze to provide that natural protection from floods. It would have been more cost effective to keep those ecosystems in place. But I hope we can learn from these lessons. I was in Beijing a month ago meeting with leaders from the Chinese Academy of Sciences who are looking at ways to reconcile economic development and ecosystem protection. And I am optimistic and hopeful that China will be able to achieve those ambitious targets for protection and that vision of ecological civilization as a day-to-day reality and not just as an ideal. And China is not alone. We just conducted a survey on 12 countries of the five different continents. And people around the world believe that we have already protected 30% of the planet. And they overwhelmingly agree that we need to protect half of the planet. Next year, we have a historic opportunity. China is hosting a historic conference of the UN Convention on Biological Diversity in the city of Kunming in October 2020. That's the place and the time where the world can come together and agree to protect at least 30% of our planet, land and seas by 2030 as a milestone. But not only governments have something to do here. Everybody can help. The World Economic Forum is launching an initiative called Business for Nature this week. And I hope that all of your companies will join and commit to it. They will advocate for the shift that I mentioned. And I know that you are not used to hear good news from scientists. But this is what I can tell you today. If we rise to the occasion, scientists will not have to ride the obituary of our planet.  Instead, we will tell stories like Cabo Pumos, stories of resurgence, stories of renewal, stories of people coming together to save the planet we love. I look forward to taking that journey with you. Thank you. Thank you, Enric. So clearly, we have a threat. We have a threat from continued destruction of ecosystems. But as you've laid out very clearly, we have an opportunity. The opportunity presented by protection protected areas. And we have a plan protecting 30% of the planet. In your opinion, what is the major roadblock? What is the main challenge on our way to actually implementing this plan of protecting 30% of the planet? Well, there are 1,000 roadblocks. I would say the main challenge is corporations don't pay for polluting. They pollute for free. And they destroy our natural capital. They destroy our life support system for free. And it is citizens who pay the cost with their well-being or their lives, as we saw in the case of the young set. So for me, one thing we need to do is to internalize the costs of our activities. It's through a carbon tax or through other types of environmental taxes where companies will have to pay for the cost that citizens would have to incur otherwise. And that means also that governments would have to think about the avoided costs. Protecting those forests and those wetlands and those grasslands along the Yangtze would have been more cost effective, less costly in terms of human lives and financial resources if they had been protected versus developed and then tried to repair something that we don't have the ability to rebuild. And all these services that nature provides for free, we cannot make them ourselves. One example is the oxygen we breathe. The oxygen we breathe is produced by bacteria in the ocean and by plants. And we did the calculation. If we had the industrial ability to produce the oxygen that is in the atmosphere now that nature produced for free, it would cost 1,600 times the global GDP. And that's just one service. So that's a big challenge that we have. Thank you. And I'd like to take questions from the audience. Yes? Ivan. Enric, thank you for taking us through the story of water. I was wondering if you could give us a few insights on the story of sand. Desertification has been, I think, accelerating in a lot of places in the world. I read that in the Middle East, they discovered a miracle bush that is able to push back desertification and create its own environment. But can you give us any sort of pointers, any hope, any interesting factoids on the desertification of the land? Any important points about the desertification of the planet? Of course, I'm not expert on deserts or the certification. But I have been to a protected area in the border of Saudi and Abu Dhabi, where the overgracing of the natural plants has been reduced because camels have been domesticated and camels, which are kind of the desert equivalent of the cows, have been taken out of the area. And the area has been re-wilded with the natural herbivores, the oryx and the gazelles of the desert. And the plants are coming back because the grazing by the natural herbivores are enhancing the growth of these plants. This is one reason why, before humans get to a place, you have these ecosystems with thousands of species and everybody co-exists. It seems that we are the only species that cannot co-exist with the rest of the planet. So these re-wilding efforts are very, very important for stopping the certification and other erosion of mounds, for example. And the re-wilding involves both replanting vegetation but also restoring the natural processes through the reintroduction of herbivores that were abandoned at one point and had been eliminated. So there are great opportunities for bringing about entire ecosystems. And we have great examples from a British farm that went from a monoculture with the soil poisoned by pesticides and fungicides. And now it's a place that cells are going to meet and people go there for safaris to see all the animals that they cannot see anywhere in the United Kingdom. Two examples in the mountains in Romania where bison are back or the walls in Yellowstone were in 1995, walls were introduced in Yellowstone National Park in the United States, and they brought back the entire ecosystem. Thanks, Eric.  But I was wondering, I think the solution for that will probably start from being able to see how much they actually pollute. But is there any central efforts or initiative or organization that tries to measure the data of who pollutes how much? Is there any kind of data sources that we can refer to that we can go back and see? Yeah, actually there is a great example in China. There is an individual called Ma Jun. He's one of the four most environmentalists in China. And he has developed this public database that you can access with your phone. And you can see the pollution by individual industries, individual plants. And that's a way to increase transparency. So Ma Jun, checking online, he's developed this amazing public database to look at pollution in China. Good evening. I'm Vanshika. I'm a global shaper from the New Delhi hub, India. So I had a few questions. Firstly, your views on what do you think of how far we've gone in terms of our negotiations with regard to climate change? So we have the new Paris climate deal, but where we're shifting from the common but differentiated responsibility CBDR approach to and what had mandatory targets to now like a voluntary approach. So instead of binding commitments, countries have to have like internally determined targets which are voluntary nature, which has some positives but also has a lot of pitfalls. So how do you think post 2020 that's going to play out? And link to that is also like climate finance, because there's so much money which is going into the sector and you'll be at the Green Climate Fund or so on. But in terms of execution or seeing the implementation of that, and especially, I mean, so the funding coming from North but like in the South countries, first is first getting that funding. And second is to have the skills and the manpower to kind of execute it. So that's another problem. So your views on that. And secondly, because if your focus was on water, we see with coral reefs in particular which are sort of the first to be hit by climate change. We see that, you know, be it El Nino or other other phenomena, there's been huge coral bleaching in the past 15, 20 years. And some people say that by 2030, 2040, we lose most of our corals. Do you think that what is that really what's going to happen or their ways to kind of? OK, yes. So coral, we are going, you know, the Paris Climate Agreement, the goal is not to exceed 1.5 degrees Celsius, right? We are already at one degree. So 1.5 degrees Celsius means the loss of 90% of the coral reefs of the world. Our climate optimum means that we are willing to lose all most of the coral reefs. In terms of the finance there, there is a lot of climate finance programs like Red Plus to enhance, foster reforestation and stop deforestation, pay performance schemes. But they haven't really worked. And people have been caching the money. And actually continue to deforestation. And Brazil is a good example. And the first, what was the first question? Oh, yeah, the countries. The countries, yes. So, you know, for climate we have this target, 1.5 degrees Celsius or 2 degrees Celsius. Everybody understood that. We cannot exceed that temperature. And that means that we have to reduce emissions. Everything else is just tactics, right? And no country came to Paris with a plan to operationalize that target. None, right? Biodiversity is much more difficult because you have 9 million species on the planet. And you have 800 different ecoregions. And it's so complicated. There are so many, so many levels. And then you have genetic resources. And until now, the biodiversity targets were so difficult that it was impossible to achieve any progress. The only target that so far has succeeded is the quantitative special targets. Until now, next year, October 2020, the goal is to achieve 10% of the ocean under protection and 17% of the land. We are on our way. And we are pushing for having 30% protected by 2030 as one of the apex targets for the convention for biodiversity, similar to the 2 degrees Celsius, right? Most countries are not going to have a plan, right? Some countries are going to take longer than others. But this will require work at the national level but also international coordination because the convention doesn't say that we need to protect 10% of every country. It's 10% of the global common, right? For example, if we care about climate change, Brazil is more important than Niger, right? The Amazon forest is more important than a desert. So it's going to be very difficult. But the first step is to agree on an apex target that everybody understands, that the politician can explain and support, and then we'll have 10 years to implement it. Oh, sorry. Wrap up in two minutes. Thanks, Eric, for sharing with us. So I'm a veggie owl from 2018. So my question is regarding, you know, you have shown that 96% of the planet is full of the mammals used for livestock and also humans. So for me, in order to maybe improve the diversity, maybe we need to cut down the demand, maybe ask more people to eat, more maybe vegetarian food. But to me, I'm okay, but how to communicate with the general public? What's the best strategy? Yeah, one of the big solutions for climate change and destruction of nature would be to eat less meat, and eat more plants. That would be also good for people's health. How to communicate this to people? Well, you know, it's very complicated. The problem is that we cannot place the burden on citizens only, right? Governments have a responsibility. Companies have a responsibility. So it's going to be very difficult to have a bottom-up action that is going to achieve the desired climate goals in time, right? So we need some regulation from governments to reduce the amount of land that is destined to grazing, for example, in the United States alone, for example, the United States, 41% of the land of the United States is dedicated to livestock, 41%. And it's not a significant proportion of the calories that the American citizens get, right? So we need both. Just let's not place all the burden on the citizens. Thank you, Enric. We're coming to the end of our time, so that was the last question. I think we've clearly made the case that this is a complex problem that touches upon all the different areas, whether it's food production, how we look at economic activity, how we take into account the ecosystem services of nature that are not valued at the moment, and that we really all need to step up our efforts because we cannot afford to lose the ecosystems. It's at our own risk, so thank you, and I hope we'll be able to count on your support to make the case to protect 30% of the planet by 2030. Thank you very much. Thank you. Thank you. Thank you very much. Thank you.